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StudioTech M45-00151 User's Manual

1. mately the same time The dual auto null mode allows a single tap of the button to initiate nulling of both hybrid circuits When configuration DIP switch 3 is in its on up position the independent auto null mode is selected This is appropriate for applications in which the two audio paths associated with the Model 45 s intercom interface are used with independent party line intercom circuits This situation might arise when two Clear Com single chan nel intercom circuits are connected to the Model 45 The hybrid circuit associated with each channel can be auto nulled as desired Another example would be in an RTS TW series application that uses source assignment panels The SAP panels would be used to route multiple intercom channels to various sets of user devices as desired In this case the two channels associated with the Model 45 s interface will often end up not routed to the same user device Independent auto nulling is certainly desired Auto Terminate Disable The auto terminate function is designed to ensure that each 2 wire to 4 wire in terface circuit remains stable under most operating conditions It can only be active when the Model 45 is not serving as the intercom power source The auto termi nate function applies 200 ohm imped ances to both pins 2 and 3 of the 2 wire party line interface when no source of DC power is detected on either of those pins This function is directly compatible w
2. are used for interfacing audio input audio output party line intercom and DC power signals The Model 45 is housed in a com pact half rack form factor that meets the needs of broadcast throw down applications Optional front panels allow one or two Model 45 units to be mounted in one space 1U of a standard 19 inch rack enclosure S N OJ D CO SE TECHN LOGIES www studio tech com CONFIGURATION SWITCHES ALLOW 2 WIRE au INPUT POWER SW1 NOV YI 2 WIRE PL POWER SOURCE SW2 OFF ON AUTO NULL Suara SW3 DUAL Y INDEPENDENT AUTO TERMINATE SW4 NORMAL Y DISABLE 4 WIRE MUTE DURING AUTO NULL SW5 NORMAL Y DISABLE 4 4 WIRE CH 2 MADE IN USA LINE IN CH 2 LINE IN CH 1 Issue Preliminary 2 March 2009 Page 5 Model 45 Interface 2 Wire Party Line Interface The Model 45 s two channel 2 wire party line interface is optimized for direct connec tion with a dual channel party line intercom Circuit In addition single channel party line intercom circuits can also be connect ed Many broadcast applications use the dual channel TW series from RTS which includes their popular BP325 belt pack The Model 45 s 2 wire interface is configured for a 10 dBu nominal level exactly matching the level of the TW series Other industry standard single and dual channel party line intercom systems including those from Clear Com are also directly compatible While their nominal level is appro
3. Ports with the Model 45 Interface 1 2 8 Position 3 Modular Plug 4 RJ 45 to To Model 45 Artist Matrix Port 5 4 Wire Output AlO 108 6 XLR F 7 To Model 45 8 4 Wire Input XLR M Back Panel Jack on 8 Position Modular Plug Matrix Chassis also known as RJ 45 Pr3 Pr3 Pr2 Pri Pr4 Pr2 Pri Pr4 12345678 Jack Front View PI Plug Top View T568B RJ 45 Wiring Release Tab on Bottom Pin 1 WHT ORG Pin 2 ORG WHT Pin 3 WHT GRN Pin 4 BLU WHT Pin 5 WHT BLU Pin 6 GRN WHT Pin 7 WHT BRN Pin 8 BRN WHT Model 45 User Guide Issue Preliminary 2 March 2009 Studio Technologies Inc Page 29 Appendix C Interfacing Clear Com Matrix Intercom System Analog Ports with the Model 45 Interface Model 45 Call Receive 1 Call Receive 2 Audio Receive 3 8 Position Modular Plug Audio Send 4 To Model 45 RJ 45 to AudioSend 5 4 Wire Input Matrix Port XLR M Audio Receive 6 Call Send T Call Send 8 To Model 45 4 Wire Output XLR F Issue Preliminary 2 March 2009 Model 45 User Guide Page 30 Studio Technologies Inc Model 45 Interface This page intentionally left blank Model 45 User Guide Issue Preliminary 2 March 2009 Studio Technologies Inc Page 31
4. figured the Model 45 can automatically switch from using the external 24 volt source to using power from the 2 wire party line circuit While this action can occur it is not designed as a power fail back up function A seamless switch over from using the external 24 volt DC input to the 2 wire party line circuit is not guaranteed The Model 45 might have a momentary power outage approximately one second before again going through the start up process Only after this process has completed will operation again commence Model 45 User Guide Studio Technologies Inc Model 45 Interface External 24 Volts as the Power Source As previously discussed the Model 45 can be powered by a source of 24 volts DC A locking 2 1 x 5 5 mm coaxial power jack is located on the back panel of the unit The center pin of the jack is the positive connection While the requirement for the external source is nominally 24 volts correct operation will take place over a 20 to 28 volt range The Model 45 requires 750 milliam peres for correct operation Approximately 500 milliamperes of this current is used for the 2 wire party line intercom power source feature Included with each Model 45 is a universal mains input 24 volt DC output power supply The power supply s DC output cable has been terminated with a Switchcraft S760K coaxial power plug This locking type of plug correctly mates with the Model s 45 s 24V DC I
5. on Model 45 User Guide Studio Technologies Inc Model 45 Interface pin 2 falls below 24 volts for a continuous 1 second interval The hardware and software responds to this condition by turning off the power source to pin 2 and flashing the pin 2 LED as a warning After a 5 second cool down interval the output returns to the same condition as upon initial power up Power is again applied to pin 2 the pin 2 status LED will light and monitoring won t begin for another five sec onds A full short circuit condition applied to the Model 45 s 2 wire connectors will result in a continuous cycle of six seconds on five seconds for start up and one sec ond for detection and five seconds off As a diagnostic aid the 2 wire PL power status LED associated with pin 3 always remains active even when the Model 45 is supplying power to the 2 wire party line intercom circuit Whenever DC in excess of approximately 18 volts is present on pin 3 the LED will light This condition will typically not exist but could prove useful in special circumstances 2 Wire Circuit Serves as the Unit s Power Source If no external source of 24 volts DC is connected and configuration DIP switch 1 is in its on up position the connected 2 wire party line circuit can provide power for the Model 45 If this condition is active the 2 wire PL input power LED will light The 2 wire PL power status LED will also be lit indicating that power
6. power source for the Model 45 It s important to remember that if an ex ternal source of 24 volts DC is connected it will always be used as the Model 45 s power source Even if switch 1 is in its on up position power will be drawn from the connected intercom circuit only if the external source of 24 volts DC is not present With that in mind it s highly recommended that unless the application has been carefully designed any time an aay A OJ D CO M TECHNSLOGIES www studio tech com CONFIGURATION SWITCHES ALLOW 2 WIRE PL INPUT POWER SW1 NO Y YES 4 2 WIRE PL POWER SOURCE SW2 OFF ONA AUTO NULL BUTTON SW3 DUAL Y INDEPENDENT AUTO TERMINATE SW4 NORMAL Y DISABLE 4 4 WIRE MUTE DURING AUTO NULL SW5 NORMAL Y DISABLE 4 Figure 6 Details of front panel showing the five configuration DIP switches and the configuration switches chart Issue Preliminary 2 March 2009 Page 16 Model 45 User Guide Studio Technologies Inc Model 45 Interface external source of 24 volts is going to be connected switch 1 should be placed in its off down position This ensures that a failure of the connected 24 volt DC source won t cause the Model 45 to automatically revert to pulling power from the intercom Circuit Some additional details might be helpful Be certain to allow only the connected intercom circuit to supply power switch 1 on if it s fully able to do so Trying to draw current from a circuit th
7. the results are stored in nonvolatile memory Once the process is complete the 4 wire input and output paths are again activated Configuration DIP switch 3 allows an independent auto null button mode to be selected If switch 3 is in its on up position the front panel pushbutton will function in quite a different manner In the independent mode a single tap to a switch will cause channel 1 to auto null Two taps will cause channel 2 to auto null By observing the operation of the two auto null status LEDs it will become readily apparent which of the button modes has been selected If possible prior to performing an auto null it s polite to warn all personnel who are ac tively using the connected intercom devic es The tones sent to the 2 wire intercom circuit during the nulling process are not excessively loud or obnoxious but most users might want to remove their headsets during the process In addition to warning users it might be a good time to ask them to mute any active microphones While the automatic mic kill signal will apply Model 45 User Guide Studio Technologies Inc to many user devices it may not apply to all Muting microphones is significant as obtaining a deep null requires that no extraneous signals be present on the inter com circuit Auto Terminate Disable As previously discussed in this user guide the auto terminate function can come into play when the 2 wire party li
8. was to identify resources that would improve the installation process and make operation more reliable This led to the use of standard 3 pin XLR type audio connectors enabling rapid installa tion and troubleshooting in any locale The inclusion of LED level meters allowed con tinuous monitoring of the input and output signals Additional status LEDs were also deemed to be valuable Configuration DIP switches would allow crucial operating modes to be selected A subtle but critical requirement was the need for the Model 45 to receive its oper ating power from either an external 24 volt DC source or the connected 2 wire party line intercom circuit It also turned out that in many applications only a small number of user devices such as belt packs were typically connected to a 2 wire party line circuit So by adding a DC power source to the Model 45 s 2 wire interface the need for an external intercom power supply could often be eliminated The final step was to create a physical package that would provide significant resources in a format that allowed simple and reliable integration with other equip ment This was accomplished by speci fying a convenient half rack form factor which would be excellent for thrown down use And by creating two 1U rack mount options it would be possible to install one or two Model 45 units in one space of a 19 inch rack Installation In this section you will be preparing the Mo
9. 4 wire outputs to be disabled When switch 5 is in its off down posi tion the Model 45 operates in its standard fashion When switch 5 is in its on up position the 4 wire outputs will not mute during the auto nulling process As ex pected when the Model 45 is deployed in the field switch 5 should remain in its off down position However no damage to the Model 45 or connected equipment will occur when muting during auto null is disabled Operation Upon power up the Model 45 will always go through a short initialization sequence before normal operation will begin The LEDs will light sequentially and upon Model 45 User Guide Studio Technologies Inc completion the applicable input power LED will light The null settings for the two hybrid circuits are recalled and used hav ing been previously stored in nonvolatile memory Significant user intervention is typically not required during normal Model 45 opera tion The unit is designed for continuous operation with no routine adjustment or maintenance necessary Assuming that the desired configuration has been select ed using the DIP switches only occasion ally activating the auto null function should be necessary The latter may be warranted should connected user devices or wiring associated with the 2 wire party line inter com circuit be changed External 24 Volt DC Power Source In many applications an external source of 24 volts DC will be connected to th
10. Model 45 Interface User Guide Issue Preliminary 2 March 2009 This User Guide is applicable for serial numbers M45 00151 and later Copyright 2009 by Studio Technologies Inc all rights reserved www studio tech com 50216 0309 Issue Preliminary 2 This page intentionally left blank Model 45 Interface Table of Contents FRO GU CMON sanoe rie e a EEEE 5 VRS TAM CIN siss Eaa aa ENE Eai 10 Confg ratloi ss sinear E EER 16 Operation gcse oe cae saeco eee eee ee 19 Technical Notas ciran 24 Specifications sais sccieseSecececzscecnecesbintancaseteniviatentviatidiateace 27 Appendix A Interfacing with RTS Matrix Intercom Systems ccncscicccscctecsscctccrecicatics iecawecct 28 Appendix B Interfacing with Riedel Artist Matrix Intercom Systems cccessceeeesesceeeeeeseeeeenaes 29 Appendix C Interfacing with Clear Com Matrix Intercom Systems asst cccctcecteite ccanct oceanesuevedenrcee 30 Studio Technologies Inc Page 3 Model 45 Interface This page intentionally left blank Issue Preliminary 2 March 2009 Model 45 User Guide Page 4 Studio Technologies Inc Model 45 Interface Introduction The Model 45 is designed to interface 2 wire full duplex party line PL intercom circuits with 4 wire audio circuits associ ated with matrix intercom systems Appli cations for the Model 45 include television sports and live event broadcasting theme park and theater installations co
11. N c 750 mA MAX PINS LOOP THRU LINE OUT CH2 LINEOUTCH1 LINE INCH 2 LINE INCH 1 24 VDC Power Supply Optional 2 Wire System 1 Party Li arty Line System 2 24 VDC Power Supply Optional Ot ee MODEL i INTERFACE 5 2 WIRE PL 4 WIRE TECHNOLOGIES INC Suaeda tech com US waves W WITH e F MADE IN USA 24V DC IN c 750 mA MAX PINS LOOP THRU LINE OUT CH2 LINEOUTCH1 LINEIN CH2 LINE IN CH 1 Figure 9 Two Model 45 units connected as a universal 2 wire to 2 wire bridge Issue Preliminary 2 March 2009 Model 45 User Guide Page 26 Studio Technologies Inc Model 45 Interface Specifications General Audio Frequency Response 2 5 dB 100 Hz to 8 kHz Distortion THD N lt 0 2 measured at 1 kHz 4 wire input to 2 wire interface pin 2 Signal to Noise Ratio gt 55 dB measured at 1 kHz 4 wire input to 2 wire interface pin 2 2 Wire Party Line PL Intercom Interface Type two channel party line unbalanced pin 1 common pin 2 DC with channel 1 audio pin 3 channel 2 audio Compatibility single and dual channel intercom systems such as from RTS and Clear Com Impedance Normal gt 10 k ohms Impedance 2 Wire PL Power Source Mode 200 ohms Nominal Level 10 dBu Mic Kill Signal square wave 24 kHz 1 2 Wire Power Source 30 volts DC nominal 300 milliamperes maximum Hybrids 2 Topology 3 section analog circuitry compens
12. N jack The locking feature is im portant allowing the external power source to be securely attached to the Model 45 A detachable mains cord is used with the power supply s 3 pin IEC 320 C14 type inlet connector Included with each Model 45 is a mains cord with a North American NEMA 15L standard plug on one end and an IEC 320 C13 type connector on the other Units intended for use in other desti nations require that the appropriate cord set be obtained from the dealer or distributor Using the Connected 2 Wire Party Line Circuit as the Model 45 s Power Source The connected 2 wire party line intercom Circuit can be used to provide the Model 45 s operating power The acceptable volt age range is 24 to 32 volts DC with a re quired current draw of 175 milliamperes Note that for the Model 45 to be powered by the connected 2 wire intercom circuit Model 45 User Guide Studio Technologies Inc configuration DIP switch 1 must be in its on up position Please refer to the Con figuration section of this user guide for additional details Before blithely going ahead and powering the Model 45 with a party line circuit it s important to review the possible pitfalls of this arrangement First of all compared to most intercom belt packs the Model 45 is a power hog requiring the aforemen tioned 175 milliamperes of DC current for operation The other requirement is that the supplied voltage must be 24 volts or gre
13. able installation Initial Operation As soon as a source of power is applied the Model 45 will begin its power up sequence As a boot up indication the input power status and meter LEDs will light one at a time in a walk through sequence After the sequence has com pleted one of the input power LEDs will light indicating which power source is actively powering the unit The Model 45 is now fully functional Configuration To support the needs of various applica tions the Model 45 allows a number of operating parameters to be configured A 5 position DIP switch assembly located on the front panel is used to establish the desired configuration Refer to Figure 6 for detailed views 2 WIRE PL odel 45 Interface STATUS INPUT AUTO POWER NULL co W IRE 1 CONFIGURATION Using the Connected 2 Wire Party Line Circuit as the Model 45 s Power Source Configuration DIP switch 1 is used to select whether or not the connected 2 wire intercom circuit can be used to provide power for the Model 45 When the switch is in its off down position the intercom circuit cannot be used to power the Model 45 This ensures that no current will be drawn from the intercom circuit some thing that can be important if the circuit is limited in available current or if the length of the interconnecting cable is excessive When switch 1 is in its on up position the 2 wire party line circuit can serve as the
14. ally been a time consuming ag gravating process requiring the efforts of an expert to achieve reasonable results And even under those constraints the resulting audio performance was often mediocre This history lesson made it clear that any new design had to start with a unique set of requirements This led to an overriding design goal create a new breed of cat fundamentally changing how broadcast 2 wire to 4 wire interface equipment fits into actual applications An important first step was to eliminate the requirement that a senior technician along with a screwdriver be present dur ing every installation It was universally acknowledged that their time can be better spent elsewhere The need to adjust trim potentiometers fabricate special cabling and connector straps use nulling ear pieces etc had to be eliminated For ex ample in virtually all instances input and output levels fall within just a few dB of their nominal values and as such could be sup ported with one industry standard nominal audio level In addition it was acknowl edged that in this application analog audio circuitry was capable of providing excellent audio performance but that the required manual nulling process was operation ally taxing By adding digital control to the analog circuitry automatic nulling could be performed the best of both worlds Issue Preliminary 2 March 2009 Page 9 Model 45 Interface The next step
15. at s not capable of supplying the needs of the Model 45 will typically result in greatly degraded intercom audio quality This is because the Model 45 s power supply circuit will always attempt to draw the current it requires If it s able to do so a constant high impedance load will be applied to the circuit and everything will perform correct ly But if the party line intercom circuit isn t capable of providing the required voltage and current the Model 45 s circuitry will become unstable and negatively impact the intercom circuit s audio quality Howls squeaks and squeals are the expected failure mode No damage will be done but intercom performance will be greatly compromised In conclusion the Model 45 can function very well using the intercom circuit as its power source But this requires that the Circuit can meet the voltage and current requirements Model 45 Provides 2 Wire Party Line Power Source Configuration DIP switch 2 is used to se lect whether or not the Model 45 will serve as an intercom power source providing DC power and 200 ohm terminations to the intercom interface When switch 2 is Model 45 User Guide Studio Technologies Inc in its off down position the Model 45 will not serve as an intercom power source This setting is appropriate when an exter nal intercom power supply is providing power and terminations to the connected 2 wire intercom user devices When switch 2 is in its on u
16. ater as measured directly at the Model 45 s 2 wire PL connectors Whether the connected party line intercom circuit can provide this much energy will depend on the characteristics of a specific installation The relevant factors include the capacity of the intercom power supply the number and type of connected user devices and the length and type of the interconnecting cables The capacity of the intercom power sup ply must meet or exceed the needs of the connected user devices including the Model 45 It s a good idea to perform a calculation of the total maximum current draw prior to attempting to install and use the unit As a real time confirmation often these power supplies have status indica tors that can provide a direct indication of their ability to supply the connected loads In many cases the length and type gauge of the interconnecting cable will be the limiting factor as to whether the intercom circuit can provide adequate power for a Model 45 This is because the intercom circuit s DC voltage will drop in direct relation to the length of the intercon necting cable And with the Model 45 s relatively large current draw this voltage Issue Preliminary 2 March 2009 Page 15 Model 45 Interface drop can become appreciable in situations where belt pack operation wouldn t nor mally be impacted Performing accurate calculations in this scenario is a bit more difficult but might be required to ensure a reli
17. ates for resistive inductive and capacitive 2 wire party line loads Nulling Method automatic upon user initiation processor implements digital control of analog circuitry null settings stored in nonvolatile memory Nulling Line Impedance Range 120 to 350 ohms Nulling Cable Length Range 0 to 3500 feet typical Trans Hybrid Loss gt 40 dB typical at 800 Hz 4 Wire Inputs 2 Type transformer coupled capacitor isolated Impedance 13 k ohms Nominal Level 4 dBu Maximum Level 22 dBu 4 Wire Outputs 2 Type transformer coupled capacitor isolated Impedance 50 ohms nominal Nominal Level 4 dBu Maximum Level 20 dBu into 2 k ohms Model 45 User Guide Studio Technologies Inc Meters 4 Function displays level of 4 wire inputs and outputs Type 5 segment LED modified VU ballistics Connectors 4 Wire Line Inputs 3 pin female XLR type 4 Wire Line Outputs 3 pin male XLR type 2 Wire PL Interface 3 pin male and female XLR type External 24 Volt DC Input coaxial power jack 2 1 x 5 5 mm locking bushing compatible with Switchcraft S760K plug Power Requirements External 24 volts DC nominal acceptable range 20 to 28 maximum required current 750 milliam peres 20 volts Universal mains input 24 volt DC power supply shipped with each unit 2 Wire Party Line when serving as source 24 to 32 volts DC 175 milliamperes Dimensions Portable Throw Down Version Overall 8 7 inches wid
18. atus column will be lit and one LED in the column associated with from 4 wire channel 1 will also be lit As previ ously described these two LEDs represent the unit s current software version After the software version number has been read the auto null button can be released At this time the unit will begin its normal power up sequence Model 45 User Guide Studio Technologies Inc Model 45 Interface Major Release Number O4 O 3 O02 i Release Sub Number 40 3 20 10 4 WIRE CH 1 2 WIRE PL PIN2 POWER Si STATUS PINs AUTO NULL cH1 le CH2 4 WIRE CH 2 Figure 8 Detail of front panel showing the status LEDs that display the software version In this example the software version is 1 3 Note that while it s easy to determine which software version is loaded into the Model 45 a trip back to the factory is required to update it The 8 bit micro controller that provides the unit s logic horsepower also includes internal FLASH memory This nonvolatile memory is used to store the operating software firmware Re programming this mem ory requires using a specialized program ming unit While not outrageous in price it still costs in the range of US 500 The pro grammer uses a ribbon cable and socket to interface with a 6 pin header on the Model 45 s printed circuit board And as you would guess once connected repro gramming takes onl
19. come from the 2 wire party line circuit and go out the 4 wire inter faces An issue may arise if the signals coming from the connected party line user devices aren t at a sufficient level so that anormal meter display can be reached This could be the result of an incorrectly configured 2 wire nominal audio level It s also possible that an error is pres ent on the 2 wire party line circuit Signal levels associated with 2 wire party line circuits depend on a single termination being present This termination typically 200 ohms is almost always made at the power supply source But it s possible that another device such as a second active power supply on the same circuit will cause a double termination condi tion This leads to a nominal 100 ohm line impedance which will result in a level drop of at least 6 dB Removing the unwanted termination is really the only valid means of correcting the problem Issue Preliminary 2 March 2009 Page 22 Auto Null The Model 45 contains circuitry to auto matically null the two 2 wire to 4 wire interfaces Normally this process is per formed at the time of initial Model 45 configuration but there s no reason why auto nulling can t be initiated anytime one desires The only time that auto null must be performed is if conditions have changed vis a vis the intercom user devices and wiring connected to a Model 45 s 2 wire PL connectors Even a slight change to an in
20. del 45 for use Since the standard unit is housed in a self contained enclosure Issue Preliminary 2 March 2009 Page 10 getting it ready for use in portable appli cations requires only making a few inter connections These include 4 wire audio input 4 wire audio output and 2 wire party line intercom connections that use 3 pin XLR type connectors In many ap plications an external source of 24 volts DC will be connected using the supplied power adapter For permanent installations one or two Model 45 units can be mounted in one of the optional rack panel adapters The resulting one rack space unit will be mounted in an equipment rack Shipping Carton Contents The shipping carton contains a Model 45 Interface a universal input 24 volt DC output power supply one set of self stick protective bumpers and a user guide A North American standard mains power cord will be provided for use with the power supply If necessary the dealer or distributor will provide an AC mains cord that is appropriate for your location Ifa rack mount front panel is going to be used as part of the installation it will typically be shipped in a separate carton Locating the Model 45 The location of the Model 45 will dictate the length of the cable runs needed to link the unit with the other required intercom devices This factor really only relates to the 2 wire party line intercom circuit These circuits carry unbalanced audio which can be su
21. e 22 1 cm 1 72 inches high 4 4 cm 8 3 inches deep 21 1 cm Mounting Options single or dual unit rack mount front panel uses one space in a standard 19 inch rack Weight 1 8 pounds 0 82 kg rack mount front panel adds 0 2 pounds 0 09 kg Specifications and information contained in this User Guide subject to change without notice Issue Preliminary 2 March 2009 Page 27 Model 45 Interface Appendix A Interfacing RTS Matrix Intercom Systems with the Model 45 Interface ADAM Matrix Intercom System Analog Ports to Model 45 Interface 9 Pin D Sub Connector Female to Matrix Port 1 gt 2 gt 6 gt A gt 2a Audio to Matrix H To Model 45 gt lt 3 4Wire Output 9 gt I NC lt 1 XLR F 8 gt gt 2 Audio from Matrix Io To Model 45 7 gt gt 3 4 Wire Input 3 gt noi XER M When connecting to ADAM CS use only low profile receptacle e g Tyco AMP part no 747516 3 RVON I O I O Connections to Model 45 Interface 9 Pin D Sub Connector Female to Matrix Port 4 Audio to RVON I O Lo To Model 45 5 gt gt lt 3 4 Wire Output gt NC lt 1 a 9 8 gt _ gt 2 Audio from RVON I O Io To Model 45 7 gt gt gt 3 4Wire Input 3 ee NC gt 1 eM Issue Preliminary 2 March 2009 Model 45 User Guide Page 28 Studio Technologies Inc Model 45 Interface Appendix B Interfacing Riedel Artist Matrix Intercom System Analog
22. e Model 45 Typically this will be in the form of the external power supply provided with the unit by Studio Technologies The 24VDC input power status LED will light whenever the external source is providing power for the unit s circuitry In this sce nario the Model 45 can be configured as to whether or not it acts as a power source for the 2 wire party line interface circuit When the Model 45 is not Serving as the 2 Wire Intercom Power Source When an external source of 24 volts DC is connected and the Model 45 is configured to not provide 2 wire party line intercom power configuration DIP switch 2 set to off the unit will not provide power to nor take power from pin 2 of the 2 wire PL connectors The 4 wire inputs and out puts as well as the internal power supply Issue Preliminary 2 March 2009 Page 19 Model 45 Interface are fully isolated from the 2 wire intercom circuit In this situation the Model 45 s only function is to route by way of the hybrids the 2 wire interface s audio signals to and from the 4 wire outputs and inputs In this mode of operation the Model 45 acts as a typical user station on the connected inter com circuit As a connection confirmation hardware and software in the Model 45 monitors pins 2 and 3 of the 2 wire PL intercom connec tors for the presence of DC voltage A level greater than approximately 18 volts DC on pin 2 will cause the status LED labeled PIN 2 to light A l
23. evel greater than 18 volts DC on pin 3 will cause the status LED labeled PIN 3 to light The author is aware that user intercom devices almost always draw power from pin 2 rather than pin 3 However in many broadcast applications power is provided on all intercom paths so that flexible chan nel assignments can be made In the ex ternal 2 wire power mode the Model 45 is simply an observer whether intercom power is present on pin 2 pin 3 or both pins 2 and 3 is not significant In order that the Model 45 s 2 wire to 4 wire interface circuits remain stable and don t generate audio artifacts an auto terminate feature is implemented This maintains a 200 ohm termination on both pins 2 and 3 as long as neither of the 2 wire power status LEDs is lit To clarify if either or both the LEDs are lit then both terminations are removed It was felt that this method would provide a fairly accurate indication that an active intercom circuit is connected In this case the 200 ohm termination is expected to be provided elsewhere typically as part of the external power supply and the Mod el 45 s termination is lifted Issue Preliminary 2 March 2009 Page 20 When the Model 45 is Serving as the 2 Wire Intercom Power Source When configuration DIP switch 2 is set so that the Model 45 provides 2 wire PL power its interface supplies 30 volts DC on pin 2 of the 2 wire PL intercom con nectors A maximum current draw of 300 mil
24. gle unit and dual unit 19 inch rack mount panels Model 45 User Guide Studio Technologies Inc Issue Preliminary 2 March 2009 Page 11 Model 45 Once the desired one or two Model 45 units have been installed in a rack mount front panel the assembly can be mounted into the designated equipment rack One space 1U or 1 75 vertical inches in a standard 19 inch equipment rack is required Secure the unit into the equip ment rack using two mounting screws per side 4 Wire Audio Inputs and Outputs Two audio line input and two audio line output signals are associated with the 4 wire interface section of the Model 45 Connections are made using standard 3 pin male and female XLR connectors Refer to Appendices A B and C for de tails on interconnecting with RTS Riedel and Clear Com matrix intercom systems 4 Wire Line Inputs As previously mentioned the Model 45 s 4 wire interface allows two analog line level audio sources to be connected The source for these signals will typically be ports on a matrix intercom system It s also possible that the signals will come from other devices such as a fiber optic or copper based audio transmission sys tem The 4 wire input circuitry is balanced capacitor coupled transformer isolated ome 7re PL COOOK PINS LOOP THRU LINE OUT CH2 LINEOUTCH1 LINE IN CH2 LINE IN CH 1 Interface and has an impedance of 13 k ohms The line inputs are op
25. gle unit rack mount Interface Interface front panel begin the process by remov ing the five screws that hold the standard throw down front panel to the Model 45 s chassis Using a Phillips screw driver remove the 4 40 flat head Phillips head machine screw which is located in approx imately the center of the front panel Then use a 5 64 inch hex wrench to remove the four 4 40 button head hex machine screws Save the screws and carefully protect and store the standard front panel for possible later use Using the screws that were just removed attach the rack adapter front panel to the Model 45 s chassis To prevent damage extreme care is required when aligning the front panel with the LEDs DIP switch assembly and auto null pushbutton switch that protrude through the Model 45 s chassis Tighten the screws only after careful inspection ensuring that all protrude through the front panel without interference The center Phillips head screw should be tightened first then tighten the remaining four The dual unit rack mount panel follows the same procedure but applies to two Model 45 units Store both of the removed thrown down front panels for possible later use Note that on the front panel graphics one unit is designated as A while the other B This is provided so that each can be easily identified during installation troubleshooting and operation Interface Figure 3 Model 45 shown in optional sin
26. h normal signal levels should find the meters lighting near their 0 dB point Signal peaks may cause the yellow LEDs to flash But a yellow LED that lights fully during normal operation will typically indicate a signal level or configu ration problem If the meters consistently display lower or higher levels than their O dB points it s possible that a configuration issue exists This would typically be related to incor rect settings on the equipment connected to the 4 wire inputs and outputs It s pos sible that although a connected 4 wire Issue Preliminary 2 March 2009 Page 21 Model 45 Interface device s nominal level matches the Model 45 s level setting its actual nominal level may be significantly different With a digital matrix intercom system this problem could be due to an incorrect configuration hav ing been made to a specific channel or port For example the RTS ADAM system has a published nominal level of 8 dBu but using its configuration software it s possible to set panels or ports to a level different than nominal The best solution in this case is to adjust the associated port on the intercom system so that its levels comply with 4 dBu This should at least in theory lead to the best system perfor mance including correct interfacing with the Model 45 But often it s impossible to clean up the levels of an existing system The to 4 wire meters display the level of signals that
27. headroom Using passive and active filters the frequency response is limited to nominally 100 Hz to 8 kHz This range was selected to provide excel lent performance for human speech while maximizing the ability of the hybrids to create substantial nulls When the Model 45 s internal DC power source is selected to provide 2 wire party line intercom pow er enhanced audio performance can also be expected The quality of the DC supply Circuit is very good with very little noise hum or hiss being added to the 2 wire connection In addition the impedance characteristics of the interface s DC powered wet channel was tailored Issue Preliminary 2 March 2009 Page 8 to be essentially identical to that of the unpowered dry channel This unique situation allows the automatic nulling Circuitry to provide excellent consistent results for both the powered and unpow ered channel Attention to detail is a hallmark of the Model 45 s design For example during the brief auto nulling process the interface channel s 4 wire input and output signals are normally muted preventing unwanted audio from reaching the connected equip ment Associated with the 2 wire party line interface is circuitry that under software control applies 200 ohm terminating impedances to the 2 wire party line circuit This along with other circuitry that moni tors DC voltages present on pins 2 and 3 of the 2 wire circuit ensures
28. in excess of 18 volts is detected on pin 2 The pin 3 LED will also light if the same condition is present on pin 3 Level Meters The Model 45 contains four 5 segment LED level meters These meters are provided Model 45 User Guide Studio Technologies Inc as a support aid during installation con figuration operation and troubleshooting The meters represent the strength of the signals coming in from and going out to the 4 wire connections The meters are or ganized in two groups each representing one input and one output They are cali brated to reflect the level in dB relative to 4 dBu This is similar to the way in which now legacy VU meters functioned As an example let s take the situation where an output to 4 wire LED labeled 0 dB is lit For this example the level on the 2 wire party line circuit is just large enough to light the O LED This indicates that a sig nal with an approximate level of 4 dBu is present on the associated 4 wire output connector Each level meter contains four green LEDs and one yellow LED The four green LEDs indicate signal levels at or below 4 dBu The top LED is yellow and indicates a sig nal that is 6 dB or greater than the 4 dBu nominal level An audio signal that causes the yellow LED to light doesn t necessarily indicate an excessive level condition but it does provide a warning that at some stage reducing the signal level may be prudent Typical operation wit
29. ital circuitry adjusts the analog hybrids to achieve their maximum return loss The nulling process takes approximately 12 seconds for each interface channel And it s important to Model 45 User Guide Studio Technologies Inc highlight that while the nulling process is automatic it only takes place upon user request The parameters obtained during the nulling process are stored in nonvola tile memory power interruptions won t require the auto nulling function to be performed again The Model 45 generates a sine wave audio tone for use during the auto nulling process The signal s frequency is soft ware controlled to maximize the ability of the hybrid circuits to reach a deep null In addition at the beginning of each auto nulling sequence a short period of 24 kHz tone is sent to the associated channel of the 2 wire party line interface This serves as a microphone disable mic kill signal for user devices such as the RTS BP325 By automatically disabling open microphones the auto nulling process can achieve a better result 4 Wire Interfaces Associated with the 4 wire portion of the Model 45 s dual channel interface are analog line level inputs and outputs These are intended to interconnect with a variety of 4 wire devices including matrix intercom systems audio over fiber trans mission systems and specialized audio equipment The input and output circuitry is transformer coupled to minimi
30. ith RTS TW series intercom applications in which the three conductors of a cable support both DC power and two channels of audio It s also compatible in situations where all three conductors of a Clear Com Issue Preliminary 2 March 2009 Page 18 single channel intercom circuit are con nected to the Model 45 In this latter case only one of the Model 45 s audio channels will be used There may be situations where it s neces sary for the two channels associated with the Model 45 s interface to be used with separate 2 wire party line circuits An ex ample of this might be where two loops of single channel belt packs such as units from Clear Com need to be connected In this case the intercom circuit s DC power will not be connected to the Model 45 but only to the user devices In this scenario a DC voltage won t be present on pin 2 or pin 3 Another example of this might be where adapter boxes with DC blocking are used to interconnect intercom circuits with the Model 45 In both these cases a DC voltage won t be present on either pin 2 or 3 and the Model 45 will automati cally apply 200 ohm terminations These terminations would be in error resulting in incorrect audio levels due to a double termination condition To prevent this problem the auto terminate function can be disabled When configura tion DIP switch 4 is in its off down posi tion the auto terminate function is active When switch 4 is i
31. liamperes is available This current is sufficient to power various intercom user devices such as small user stations and belt packs A common broadcast appli cation would be to use RTS BP325 belt packs Select the connected devices so that their total current doesn t exceed 300 milliamperes That s not always the easi est figure to calculate but a web search will generally find specifications for all commonly used devices For example a search finds that the original version of the BP325 consumes a maximum of 85 milliamperes of current According to this figure up to three of these units can be connected to each Model 45 Interface Newer versions of the BP325 use surface mount component technology and have a lower maximum current draw of 65 mil liamperes Four of these modern BP325 units can easily be supported The Model 45 s intercom power supply circuit operates under software control This allows detection of fault conditions and protection of both the Model 45 s circuitry and connected intercom user devices Upon initial Model 45 2 wire inter com power up no monitoring of the inter com power output takes place for a period of five seconds This allows the Model 45 s circuitry and the connected intercom user devices to stabilize The LED associ ated with pin 2 will light to indicate that the output is active After this initial 5 second period monitoring becomes active A fault condition is detected if the power
32. n pin 2 and common on pin 1 The Model Model 45 User Guide Studio Technologies Inc 45 s 2 wire party line interface can also serve as an intercom power source and 200 ohm impedance generator allowing intercom user devices to be directly con nected The Model 45 s internal 30 volt DC intercom power source is limited to 300 milliamperes of current This moder ate amount of power requires that the type and number of connected user devices be selected appropriately For convenience the 2 wire party line intercom circuit or user devices can be connected to the Model 45 by way of either a male or female 3 pin XLR type connector both of which are located on the back panel Refer to Figure 4 for a detailed view The two connectors are wired in parallel multed and provide access to the identical signals Dual Channel Intercom Systems If compatibility with RTS TW series is desired the mating connector one male or one female should be wired so that common is on pin 1 DC with channel 1 audio is on pin 2 and channel 2 audio is on pin 3 This wiring scheme applies whether the connected devices are to be powered by an external source or by the Model 45 s internal 2 wire intercom power source Single Channel Intercom Systems There are two ways of connecting to the Model 45 s 2 wire PL intercom connec tors when compatibility with Clear Com single channel intercom devices is de sired The most direct method i
33. n its on up position the auto terminate function associated with each interface is disabled The auto terminate disable function should be used only when absolutely necessary it s possible that a significant downside could be experienced With auto terminate disabled it s important that properly termi nated 2 wire party line intercom circuits be connected to pins 2 or 3 of the Model 45 s 2 wire PL interface If they are not con nected it s likely that audio oscillations noise and distortion will be generated in Model 45 User Guide Studio Technologies Inc Model 45 Interface the Model 45 s 2 wire to 4 wire converter circuitry These audio artifacts will not cause any damage but will be sent out of the 4 wire line outputs Users of the 4 wire equipment may be less than pleased with what they hear 4 Wire Mute during Auto Null As part of the auto nulling process audio tones are generated and sent out the 2 wire intercom interfaces These tones depending on the nulled state of the hybrid circuits will also appear on the outputs of the 4 wire interface circuits To prevent these unwanted tones from being sent to the inputs of the connected 4 wire devices by default the 4 wire outputs mute when the auto nulling process is active There may be cases primarily at the fac tory where it s desirable to have the null ing tones appear on the 4 wire outputs Configuration DIP switch 5 allows the mut ing of the
34. ne interface is configured to not supply power Using a combination of hardware and software pins 2 and 3 of the 2 wire PL intercom connector are monitored for the presence of DC voltage If a level of greater than ap proximately 18 volts DC is not detected on either pin 200 ohm terminating networks are applied to those same pins This en sures that the Model 45 s hybrid circuitry remains stable preventing objectionable audio signals from being sent to the 4 wire output connectors One caveat does ap ply there may be a few seconds of severe noise whenever an interface moves from a DC present condition to a DC not present condition But other than that period the audio paths will remain clean As a visual aid LEDs on the front panel will display the DC power status of pins 2 and 3 But when auto terminate disable mode is active configuration DIP switch 4 set to on the LEDs will no longer indicate the intercom circuit s termination status For special applications the auto terminate function can be disabled This will primar ily come into play when splitting the Model 45 s resources into two separate single channel interfaces Moving con figuration DIP switch 4 to its on up posi tion disables the auto terminate function To someone observing only the Model 45 s front panel this change would not be Issue Preliminary 2 March 2009 Page 23 Model 45 Interface readily apparent The front panel LED
35. nector In many applications the Model 45 will be powered by an external source of 24 volts DC A compact lightweight 24 volt DC out put power source is supplied with each unit The power supply s universal mains input capability 100 230 volts 50 60 Hz allows operation virtually anywhere in the world The Model 45 can also be powered by the connected 2 wire party line intercom circuit The four LED meters previously mentioned make it simple to confirm operation of the connected 4 wire inputs 4 wire outputs and 2 wire party line circuit Additional LED status indicators are also provided offering a clear view of the 2 wire DC power source auto null functions and input operating power The Model 45 is housed in a rugged lightweight aluminum enclosure that is designed to be road tough The half rack unit is ready for portable or stand alone thrown down applications Optional 1U front panels allow one or two Model 45 units to be mounted in one space of a standard 19 inch rack enclosure Model 45 User Guide Studio Technologies Inc Design Philosophy While the bits and pieces that make up the Model 45 have been described in con ventional terms the real strength of the unit rests in the way it integrates and performs in the real world Studio Technologies learned from conversations with indus try experts that installing and configuring 2 wire to 4 wire interface equipment has tradition
36. nergy requirement With the 2 wire interface s ability to supply up to 300 milliamperes of current a typical broadcast application which uses two or three BP325 belt packs can easily be sup ported The circuitry s output regulation is such that little change in the output volt age will occur over its entire rated output current The power source is an industry standard 30 volts DC helping to ensure that applications requiring long intercom cable runs will function correctly Also the design of the power supply circuitry helps to minimize the noise and hiss often associated with intercom power supplies Under software control the DC power supply s output is monitored for over cur rent and short circuit conditions This allows protection shut down of the output DC as well as providing an alert by way of a visual indicator An auto terminate function ensures that should a party line circuit not be connect ed the Model 45 s interface circuitry will remain stable This unique feature makes certain that objectionable audio signals such as oscillations and squeals will rarely be sent to the connected 4 wire device Analog Hybrids with Auto Nulling A key reason that the Model 45 achieves excellent audio performance is the design Model 45 User Guide Studio Technologies Inc Model 45 Interface of its 2 wire to 4 wire hybrid circuits Each of the two independent circuits provides low noise and dis
37. oth 3 pin male XLR connectors Pin 2 of the female XLR will go to pin 3 of the male XLR desig nated as channel 1 Pin 3 of the female XLR will go to pin 3 of the male XLR designated as channel 2 Refer to Figure 5 for details Using this adapter the Model 45 can be directly interconnected with two Clear Com intercom circuits However power for the connected devices must be provided by ex ternal power sources The Model 45 s ability to supply intercom power will not be utilized Note It s critical that the correct configura tion settings be made when using the Model 45 s interfaces to support two independent intercom circuits Specifically the 2 wire power source configuration DIP switch 2 Issue Preliminary 2 March 2009 Page 14 Figure 5 Adapter cable wiring diagram must be set to its off down position In addition switch 4 auto terminate disable must be placed in its on up position Refer to the Configuration section of this user guide for details Model 45 Power Source The Model 45 requires power for operation of its internal circuitry This can be provided by an external source of 24 volts DC or by way of the connected 2 wire party line circuit As you might expect if the Model 45 is to serve as the 2 wire party line power source an external source of 24 volts DC must be connected When a 24 volt DC power source is connected it always takes priority And depending on how the Model 45 is con
38. own position When switch 5 is in its on up position 4 wire muting dur ing auto null will not take place While not appropriate during actual Model 45 use it Issue Preliminary 2 March 2009 Page 24 is interesting to hear the nulling process take place But unless there s a really good reason configuration DIP switch 5 should always remain in its off down position Technical Notes Software Version Display A special Model 45 power up sequence allows the unit s software version number to be displayed This is useful when work ing with factory personnel on application support and troubleshooting situations The five from 4 wire LEDs are used to display the major release number with a range of 1 through 5 The five LEDs associated with to 4 wire channel 1 are used to display the release sub number which ranges from 1 through 5 Refer to Figure 8 for a detailed view of the LEDs and the corresponding software version numbering scheme The Model 45 s initial software release is ver sion 1 1 which is represented by the bot tom LED of each column being lit To display the Model 45 s software version is very simple From the powered down state press and hold the auto null button While continuing to press the auto null but ton apply power either by connecting an external 24 volt DC power source or a pow ered intercom circuit The normal power up sequence will not occur but instead one LED in the st
39. p position the Model 45 can provide the intercom power source with the requirement that an external source of 24 volts DC is connected to the Model 45 Auto Null Button Operation A pushbutton switch located on the Model 45 s front panel is used to activate the auto nulling functions A configuration parameter allows selection of the button s operation The choices are dual auto null mode and independent auto null mode When dual auto null mode is selected a single tap press and release on the pushbutton switch initiates a routine that begins with channel 1 s auto null sequence followed immediately by channel 2 s auto null sequence The independent auto null mode allows the auto null function to be initiated for each channel as desired A single tap will start the auto null routine for channel 1 two taps will start the routine for channel 2 When configuration DIP switch 3 is in its off down position the dual auto null mode is selected This is provided spe cifically for cases where the Model 45 s 2 wire party line interface will be used with dual channel intercom user devices As an example the RTS TW series provides two independent audio channels as well as power over a single 3 conductor cable In a case such as this it s useful for both of the hybrid circuits associated with an Issue Preliminary 2 March 2009 Page 17 Model 45 Interface interface to be auto nulled at approxi
40. rporate AV and industrial testing environments The unit provides one full featured two channel 2 wire to 4 wire interface The interface features hybrid circuitry that includes automatic nulling capability The analog hybrids under software control provide excellent audio quality and high return loss The Model 45 can be powered by an ex ternal source of 24 volts DC The circuitry is designed so that full isolation from the connected party line circuit is maintained 4 WIRE CH 1 PIN 2 6 STATUS PIN 3 0 AUTO 6 NULL 12 EEEREN 18 CONFIGURATION Interface 2 WIRE PL POWER INPUT POWER 24VDC 2 WIRE PL Figure 1 Model 45 Front Panel MODEL 2 NTE AESCe 2 WIRE PL TECHNOLOGIES INC www studio tech com 21x5 5 mm MATES WITH IN 750 mA MAX PINS LOOP THRU CE Figure 2 Model 45 Back Panel Model 45 User Guide Studio Technologies Inc LINE OUT CH2 LINE OUT CH 1 The connected party line intercom circuit can also provide the Model 45 s operat ing power For maximum flexibility the unit is capable of supplying 30 volt DC power and AC terminations thus creating a 2 wire party line intercom circuit This allows direct support for devices such as intercom belt packs Configuration settings allow the Model 45 s performance to be optimized Audio level meters provide user confirmation of system performance during setup and operation Standard audio connectors
41. s to pre pare a male or female 3 pin XLR mating connector so that common is on pin 1 power is on pin 2 and audio is connected on pin 3 With this connection scenario only audio channel 2 associated with Issue Preliminary 2 March 2009 Page 13 Model 45 Interface pin 3 of the Model 45 s 2 wire party line a a T intercom interface will be utilized Pin 2 Mogel 45 4 ie Siar afi the Model 45 s audio channel 1 will only Connector 4 S s1 LRM be used for connecting DC power to the ore connected devices While the audio resourc 3 to es provided by channel 1 will not be used oe Fe the Model 45 can still be used to supply DC 1 XLR M power on pin 2 As previously mentioned the maximum current draw on the 30 volt DC output is 300 milliamperes Alternatively an external intercom power supply can support the connected devices In some single channel 2 wire party line intercom system applications it may be desirable to take full advantage of the two channels associated with the Model 45 s in terface The Model 45 can certainly be used in this fashion but an adapter will need to be prepared The recommended connection method is to create an adapter that splits Model 45 s 2 wire PL intercom connector into two 3 pin XLR connectors one for each audio channel The adapter should use one female and two male connectors Pin 1 ofa female 3 pin XLR intended to mate with the Model 45 will connect to pin 1 of b
42. s will continue to display the DC power status of pins 2 and 3 But whether or not either or both LEDs are lit the Model 45 will never apply 200 ohm terminations to pins 2 or 3 For the hybrid circuits to remain stable termination impedances must be provided by the connected circuits If these are not present one might find the hybrid circuits generating very unpleasant audible noise This condition caused by the 2 wire out put circuitry being in an unloaded state will not damage the Model 45 s circuitry However without the auto terminate func tion a disconnected cable or other real world wiring problem could present users with a rude surprise In conclusion it s important that technical personnel working with the Model 45 be informed when the auto termination func tion has been disabled They will then be aware of the potential noise issues and be ready to make corrections should a prob lem arise 4 Wire Mute During Auto Null Normally the 4 wire outputs are muted whenever the auto null process is taking place This ensures that the test tones generated as part of the nulling process will not be heard by users of the signals associated with the 4 wire outputs For special applications configuration DIP switch 5 allows the automatic muting mode to be disabled This mode is pro vided primarily for use by factory person nel or during demonstration use During normal operation switch 5 should remain in its off d
43. sceptible to interference and crosstalk issues And since party line intercom circuits typically carry DC power a voltage drop due to resistive loss can become an issue In general minimizing the length of the 2 wire party line intercom Model 45 User Guide Studio Technologies Inc Model 45 Interface cables will help to ensure more reliable and consistent intercom system performance The differential balanced 4 wire circuits are typically not impacted by the length of their interconnecting cables A final location criterion is to provide access to the Model 45 s front panel An optimal location will allow convenient use of the auto null push button and easy observation of the level meters and status LEDs Protecting the Enclosure The Model 45 is shipped as a self contained unit suitable for portable use Included with the unit are self stick bump on protec tors These may be applied to the bottom corners of the unit if it is going to be placed on surfaces where scratching of either the Model 45 or the surface could take place Rack Mounting the Model 45 For permanent or mobile applications it s possible to mount one or two Model 45 units into one space of a 19 inch rack enclosure Two rack mount front panels purchased separately are available from Studio Technologies Refer to Figure 3 for details The following provides details on how to install and use the panels To attach a Model 45 unit to a sin
44. tercom circuit such as adding or removing a section of cable is sufficient to require that the auto null process be performed A pushbutton switch is provided to activate the auto null process Refer to Figure 7 for a detailed view To initiate auto null requires simply pressing and releasing tapping the button The process begins by nulling channel 1 of the interface and when completed moves on to channel 2 Two LEDs provide a visual indication of the auto null process flashing when the auto null process for its respective channel is active 2 WIRE PL PIN2 POWER aad STATUS PIN3 AUTO NULL cH1 Lo CH2 012345 fom ONFIGURATION Figure 7 Detail of front panel showing auto null section Model 45 User Guide Studio Technologies Inc Model 45 Interface An auto null sequence begins with the muting of the 4 wire input and output signal paths associated with the channel being nulled This is followed by a short period of 24 kHz signal that is sent out the 2 wire party line intercom interface channel This will turn off microphones on those connected user devices that are compatible with the RTS TW series mic kill protocol The actual auto null ing process is performed next A series of tones will be sent out the 2 wire interface Other Model 45 circuitry under software control will rapidly perform adjustments to achieve the best null possible After the adjustments have been made
45. that audio instability associated with unterminated circuits will rarely occur Special Applications While the Model 45 is designed to directly integrate into typical applications it s ready to support the one in a million situations too To accomplish this five DIP switches accessible on the front panel allow control over some of the unit s features For example one DIP switch changes the way the auto null pushbutton switch operates Normally pressing the button begins the process of auto nulling both channels The alternate switch mode allows each auto null sequence to be activated independently One tap of the auto null button will begin the auto null process for channel 1 Two taps of the button will begin the auto null process for channel 2 Another DIP switch allows the auto terminate feature to be disabled While this feature can help maintain Model 45 User Guide Studio Technologies Inc Model 45 Interface audio quality advanced users might need to disable it This would allow full control over the Model 45 s two hybrid circuits enabling them to be used in a completely independent manner Simple Installation The Model 45 uses standard 3 pin XLR type connectors allowing convenient 2 wire party line and 4 wire interconnection in broadcast and general audio environments For flexibility access to the 2 wire party line intercom interface can be made using either a male or female XLR con
46. timized for signals that have a nominal level of 4 dBu Audio sources are connected to the line inputs by way of 3 pin female XLR type connectors which are located on the Model 45 s back panel Refer to Figure 4 for a detailed view Prepare the mating connectors males so that XLR pin 2 is signal high or hot pin 3 is low or cold and pin 1 is shield If connecting a source in this manner results in hum or noise it s possible that removing the shield connection from pin 1 can eliminate the issue floating pin 1 will remove a ground current path from the Model 45 s chassis ground point through the shield of a cable Pin 1 on each of the two input connectors is inter nally connected to the Model 45 s earth chassis ground point Also if a hum or noise issue does arise be certain to con firm that unless absolutely necessary the mating connector s shell isn t connected to the cables shield or pin 1 Termination of this fourth pin of a 3 pin XLR connec tor is often the cause of seemingly inexpli cable noise issues With an unbalanced source connect XLR pin 2 to signal high or hot and both pins 1 and 3 to shield If connecting an Figure 4 Detail of back panel showing line inputs and outputs Issue Preliminary 2 March 2009 Page 12 Model 45 User Guide Studio Technologies Inc Model 45 Interface unbalanced source in this manner results in hum or noise connect XLR pin 2
47. to high or hot and pin 3 to shield leave pin 1 unterminated 4 Wire Line Outputs The Model 45 s dual channel interface pro vides two analog line level audio outputs These outputs are intended to be connect ed to inputs on the devices associated with the 4 wire audio signals The outputs are capacitor coupled transformer balanced with a nominal level of 4 dBu The 4 wire line outputs are capable of driving inputs that have impedances as low as 600 ohms however connecting to loads of 2 k ohms or greater is preferred The line outputs are connected by way of 3 pin male XLR type connectors which are located on the Model 45 s back panel Refer to Figure 4 for a detailed view The mating connectors females should be prepared so that signal high or hot is expected on XLR pin 2 Signal low or cold should be expected on XLR pin 3 The cables shields can be connected to XLR pin 1 However in order to minimize the chance that ground interaction prob lems will arise pin 1 on each of the line output connectors is isolated from all Mod el 45 circuitry and ground points Floating pin 1 virtually eliminates the chance that a ground loop problem will occur 2 Wire Party Line Intercom Connections The Model 45 s 2 wire party line intercom interface is designed to connect with a standard single and dual channel party line intercom circuit This type of circuit typically has positive 28 to 32 volts DC o
48. tortion good frequency response and high return loss nulling even when presented with a wide range of 2 wire party line conditions Unlike tele phone line POTS oriented DSP based hybrid circuits the Model 45 s analog circuitry provides extended frequency response With a pass band of 100 Hz on the low end and 8 kHz on the high end natural sounding voice signals can be sent to and received from the 2 wire party line circuit A hybrid s ability to isolate the transmit signal from the receive signal in the 2 wire to 4 wire interface is critical The quality of this isolation technically known as return loss or trans hybrid loss is measured in dB A high value is important especially in applications where multiple 2 wire to 4 wire interfaces are used together Remote sports broadcast applications are especially sensitive to this require ment The Model 45 s sophisticated auto nulling function uses analog circuitry under microprocessor control to achieve significant trans hybrid loss This return loss null is achieved by making a set of adjustments to account for the resistive inductive and capacitive conditions that are present on the connected 2 wire party line circuit The party line s conditions are the sum of the impact made by the type and quantity of cable the connected user devices and the intercom power source Whenever a user presses the Model 45 s auto null pushbutton switch dig
49. ximately 4 dB lower 14 dBu their greater dynamic range tends to compensate for any opera tional differences The Model 45 s 2 wire party line interface is typically connected to a powered wet unbalanced intercom circuit Powered party line circuits have a DC voltage pres ent typically provided by power supplies from RTS or Clear Com This DC power normally 30 32 volts provides energy for connected devices such as user stations or belt packs A configuration setting is used to select how the Model 45 will impact the connected 2 wire circuit In the default mode the Model 45 s circuitry maintains a high impedance load and draws no power from the party line circuit An alter nate mode allows the power required by the Model 45 s circuitry to be supplied by the connected party line circuit A significant capability of the Model 45 s 2 wire interface is its ability to create a fully functioning 2 wire party line intercom cir cuit supplying the required DC power and 200 ohm AC terminations Referred to as the Model 45 s 2 wire PL power source Issue Preliminary 2 March 2009 Page 6 mode the 30 volt 300 milliampere maxi mum output can power devices such as user stations and belt packs In many applications this will eliminate the need for an external intercom power supply Besides reducing total system cost this feature can also lower system weight reduce required mounting space and decrease the mains e
50. y a matter of seconds But unfortunately the programmer is not something that would be found in a typical field shop or repair facility Model 45 User Guide Studio Technologies Inc Two Units can be a TW 12B Replacement Two Model 45 units with their 4 wire in terface connectors linked in a crossover fashion can act as a universal 2 wire to 2 wire bridge This should in theory create an updated and improved version of the venerable Clear Com TW 12B unit In this arrangement two independent 2 wire party line intercom systems can function as one while still maintaining full electrical isolation The connection scheme is very simple using just four male female 3 pin XLR patch cords The 4 wire outputs of the first Model 45 would be connected to the 4 wire inputs on the second Model 45 the 4 wire outputs on the second Model 45 would connect to the 4 wire inputs on the first Model 45 A 2 wire party line intercom circuit would connect to each Model 45 Issue Preliminary 2 March 2009 Page 25 Model 45 Interface unit Power can be provided by the con nected intercom circuits or by way of an external source of 24 volts DC The final step to achieve correct performance is for the auto null function on each Model 45 to be activated Refer to Figure 9 for details MODEL as event 2 5 2 WIRE PL _ 4 WIRE TECHNOLOGIES INC WWW To tech com aes vir MADE IN USA O ce 2av D ff I
51. ze the chance of hum noise or ground loop issues The nominal input and output levels are 4 dBu helping to ensure compatibility with professional audio equipment Some digital matrix intercom systems use other nominal levels but with their configuration flexibility they can be easily adjusted to match the Model 45 For example the Riedel Artist system has a nominal level of 6 dBu so an adjustment Issue Preliminary 2 March 2009 Page 7 Model 45 Interface of only 2 dB is required The RTS ADAM series of matrix intercom systems has a nominal level of 8 dBu This level also applies to their RVON I O VoIP products As such reducing their nominal input and output levels by 4 dB will ensure optimal compatibility The Model 45 contains four 5 segment LED level meters with two displaying the level of the signals being received on the 4 wire inputs and two displaying the level being sent out the 4 wire outputs During installation and setup the meters are in valuable in helping to confirm that proper operation is taking place The meters are also useful during normal operation allow ing confirmation of audio signal flow into and out of the Model 45 Pro Audio Quality The Model 45 s audio circuitry was designed in the spirit of professional audio equipment rather than that found in typical party line intercom gear High performance components are used throughout providing low distortion low noise and high

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