372 SPL Computer
Contents
1. Setup Is Locked Press and hold CAL while rotating ADJUST The front panel is now unlocked 21 Symetrix 372 SPL Computer User s Guide Calibrating the 372 To calibrate the 372 1 Choose a time when the ambient Whenever the SPL of the environment Only perform calibration when the noise in the area being controlled is at this level the program channel setup for the 372 is unlocked See is at a typical level of the 372 will be at 0 dB Unity Setup Unlocked in section System 2 On the front panel press CAL gain As the ambient SPL becomes Setup Pressing CAL when the setup less the 372 lowers its gain Con is locked causes the 372 to report the The 372 reads the current _ versely when the SPL increases the most current relative calibration level ambient level and equates this gain of the 372 increases No settings are altered reading to 0 dB Unity gain 3 When calibration is finished the 372 displays the relative ambient SPL reading which it considers as Normal 22 Symetrix 372 SPL Computer User s Guide Conditions Under Which the 372 Because the 372 uses the speakers of a sound system as sensing micro phones the sound system is briefly disabled every time a reading is taken To keep these interruptions to a minimum the 372 follows several rules to prevent sensing under specific conditions Will Not Sense The 372 Will Not Take Samples When In Music mode whenever the program audio is above the G2. POWER SUPPLY ONLY BO Slave Group up to 20 units Connect a cable from TRIGGER and Ground terminals of the master unit Connect the other end of the cable to the TRIGGER input and Ground terminals of each slave unit in parallel From the front panel of the slave 372 LCD menu display Press NEXT to gain access to Operating Mode Rotate ADJUST to select Slave mode Press NEXT to locate Trigger Input Check to see that Force Sense is selected Force Sense is the default setting See Operating Mode Slave in the section System Setup for additional information 11 Symetrix 372 SPL Computer User s Guide Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing Master 372 Q Use an External Relay To connect more than 20 slave 372 units together from the master unit to sense at the same time in adjacent or multiple installation zones TO SPEAKER SENSE TRI EXT REL
3. Symetrix 372 SPL Computer 372 SPL COMPUTER 372 SPL Computer User s Guide January 2001 Symetrix Inc All rights reserved Printed in the United States of America Symetrix Part Number 53372 0C00 The information in this guide is subject to change without notice Symetrix Inc shall not be liable for technical or editorial errors or omissions contained herein nor is it liable for incidental or consequential damages resulting from the furnishing performance or use of this material Mention of third party products is for in formational purposes only and constitutes neither an endorsement nor a recommen dation Symetrix assumes no responsibil ity with regard to the performance or use of these products Under copyright laws no part of this user guide may be reproduced or transmitted in any form or by any means electronic or mechanical without permission in writing from Symetrix Inc If however your only means of access is electronic permission to print one copy is hereby granted Permission to copy the Architects and Engineers Specificiations for written proposals specifying equipment for sound reinforcement systems is also granted Symetrix Inc 6408 216th St SW Mountlake Terrace WA 98043 USA Tel 425 778 7728 Fax 425 778 7727 Web www symetrixaudio com Email symetrix symetrixaudio com Symetrix 372 SPL Computer User s Guide Before You Begin What Ships in the Box Getting
4. PS 3 OR PS 3E Waar 2 S HHHHHHHHHHHH 9 Overview of Rear Panel Connectors and Connections CONNECTION CONNECTOR TYPE WHAT IT DOES Power Input 7 pin DIN connector Accepts power only from Symetrix PS 3 or PS 3E power supply FROM AMP 2 terminal barrier strip Accepts signal from power amplifier This output may be grounded or bridged 8A maximum current rating If your speaker load exceeds the following ratings you will need to use an external relay See Connecting an External Relay to Attach Slaves MAX AMPLIFIER OUTPUT RATINGS 16 ohms 400W 70V 300W 8 ohms 200W 4 ohms 100W TO SPEAKER 2 terminal barrier strip Delivers signal to loudspeaker system Do not ground either of these terminals SENSE ExT RELAY Euroblock terminals Open collector drive signal for exter nal sense relay Can power amplifiers larger than 200W at 8 ohms See Connecting an External Relay to Attach Slaves Controls as many as 20 slave 372 units directly from the ExT RELAY output of the master 372 This output can also drive the TRIGGER input GROUND Euroblock terminals Ground return for external relay and trigger TRIGGER Euroblock terminals Active low input forces sense event Can force or prevent a sense event manually See Connecting a Push Button Switch to Force or Prevent Sensing Is i
5. output These speakers are required The relay contacts handle 8A continuous current FROM AMP TO SPEAKER SENSE LINE OUTPUT RIGHT LEFT CONNECT B ekee Hik Input Source Amplifier Connect all speakers that do not sense to the amplifier output Use these speakers for only music or paging These speakers are optional Symetrix 372 SPL Computer User s Guide Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing Connecting an External Relay to Drive Amplifiers Larger than 200W When controlling amplifiers larger than 200W you must use an external relay The internal relay of the 372 cannot handle more than 8A of Low load current 6 Low High 4 RECOMMENDED MAXIMUM nan S AMPLIFIER WATTAGES 1N4002 or T Equival 400W 16 ohms ES Jd 300W 70V ca Power 200W 8 ohms Supply 100W 4 ohms T You must supply power for t
6. Help Optional Rackmount Accessories Notational Conventions in this User Guide Operational Safety Summary Equipment Markings Features of the 372 Checklist of Tasks for Hardware Connections System Setup and Calibration Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing System Setup Overview of Front Panel How System Setup Works Description of Menu Features Operating Mode Status History Listen Set MIN Limit Set MAX Limit Averaging Time Gain Sense Ratio C WN N NNN O0 10 11 12 13 14 14 15 16 16 18 18 18 19 19 19 19 Contents Gap Threshold Force Sense Time AGC Trigger Input Setup Unlocked Calibrating the 372 Conditions Under Which the 372 Will Not Sense Signal Flow Diagram Input and Output Connector Wiring Troubleshooting Hardware Specifications Architects and Engineers Specifications Warranty Service Declaration of Conformity 20 20 20 21 21 22 23 24 25 26 28 29 30 31 32 Symetrix 372 SPL Computer User s Guide Before You Begin What Ships in the Box Getting Help Optional Rackmount Accessories Notational Conventions in this User Gui
7. MIN Limit 19 Symetrix 372 SPL Computer User s Guide System Setup Overview of Front Panel How System Setup Works Description of Menu Features Description of Menu Features continues ROTATE ADJUST TO SELECT VALUE OR PRESS NEXT TO SELECT MENU FEATURE CHOICE DESCRIPTION Gap Threshold Select value To set the minimum signal level needed for the 372 to not detect silence in the program channel In Music mode the 372 senses anytime that the music program level falls below the Gap Threshold setting If there are no gaps in the program then the 372 senses at the interval set by the Force Sense Time which ranges from never to 30 minutes See Force Sense Time In Page mode the 372 senses when directed by the Force Sense Time or by an external trigger source Use Gap Threshold to prevent sensing activity during paging If a page is in progress the 372 will not interrupt it for sensing Force Sense Time To force a sensing period when the program mate rial is too dense to contain sufficient gaps for silence sensing Never 1 3 5 Selections in Music mode 10 20 or 30 minutes Sense After Page Selections in Page mode 1 3 5 10 20 or 30 minutes Choose Sense After Page in situations where paging is frequent and uninterruptible This selection triggers a sense period about 20 seconds after the paging signal level falls below the Gap Threshold setting You can also force a sense period manually by using
8. if line input signal may be too hot Check if page mic signal may be too hot Check if the sound system has sufficient power for the SPL that you are trying to attain If using a high setting for Set MAX Limit you may be overloading the input to your amplifier select a lower value Check if something else is clipping in the signal chain Noise hiss Check input signal levels and level control settings Check gain settings on downstream equipment for presence of noise in input signal No audio Check if the unit is plugged in Check if the unit is in Listen mode 27 Symetrix 372 SPL Computer User s Guide Hardware Specifications Input Output Maximum Input Level 20 dBu balanced 20 dBu unbalanced Program Input Impedance gt 20k ohms balanced gt 10k ohms unbalanced Input Common Mode Rejection gt 40 dB line inputs Maximum Output Level 26 dBu balanced 20k ohm load 22 dBm balanced 600 ohm load Output Impedance 200 ohms balanced 100 ohms unbalanced Performance Data Program Frequency Response 20 Hz to 20 kHz 0 1 dB Program Path THD N lt 025 4 dBu in 4 dBu out Output Gain 20 30 dB Sense Channel Frequency Response 3 db at 300 Hz and 6000 Hz 3 pole Butterworth Sense Channel Gain selectable unity 20 dB 40 dB Additional Headphone Monitor Gain 28 dB maximum Program Channel Output Noise 95 dBu unity gain typical Connections Program Inputs Outputs Euroblock Power In 7 pin DIN External Trigger External Rela
9. leave the 372 physically connected in the signal path only pass the signal unaltered and never take SPL samples This feature is useful if you encounter setup problems in an installation You can temporarily disable the 372 until you have the time to correct the problem Or when the action of the 372 is temporarily unwanted for example when an unusual event is taking place You can view your control settings in this mode Any changes you make to your control settings in this mode will not take effect The gain is always held at unity 0 dB in Bypass mode Bypass mode is not a hard wire bypass 17 Symetrix 372 SPL Computer User s Guide System Setup Overview of Front Panel How System Setup Works Description of Menu Features Description of Menu Features continues ROTATE ADJUST TO SELECT VALUE OR PRESS NEXT TO SELECT MENU FEATURE CHOICE DESCRIPTION Status Cal Level Min Level Max Level Displays the current calibration status of the 372 Ambient signal level measured at the last sense period Minimum gain that the 372 is permitted to have Maximum gain that the 372 is permited to have History Reset to Zero Displays numeric readings of the highest and lowest SPLs from whenever the 372 unit was calibrated or from when the setting was last reset Resetting the 372 to Zero starts a new history period where the 372 begins to collect the highest and lowest relative SPL readings Lis
10. replacement is carried out Symetrix may at its option require proof of the original date of purchase dated copy of original retail dealer s invoice Final determination of warranty coverage lies solely with Symetrix Products repaired under warranty will be returned freight prepaid via United Parcel Ser vice by Symetrix to any location within the Continental United States Outside the Continental United States products will be returned freight collect The foregoing warranties are in lieu of all other warran ties whether oral written express implied or statutory Symetrix Inc expressly disclaims any IMPLIED warran ties including fitness for a particular purpose or mer chantability Symetrix s warranty obligation and buyer s remedies hereunder are SOLELY and exclusively as stated herein This Symetrix product is designed and manufactured for use in professional and studio audio systems and is not intended for other usage With respect to products purchased by consumers for personal family or household use Symetrix expressly disclaims all implied warranties including but not limited to warranties of merchantability and fitness for a particu lar purpose Warranty This limited warranty with all terms conditions and disclaim ers set forth herein shall extend to the original purchaser and anyone who purchases the product within the specified warranty period Symetrix does not authorize any third party including any
11. zones This mode senses only in response to an external sense command received by way of the TRIGGER input connector on the rear panel of the slave As many as 20 slave 372 units may be controlled directly from the EXT RELAY output of the master 372 Connect a cable from ExT RELAY and Ground terminals of the master unit to the TRIGGER input and Ground terminals of each slave unit in parallel See Connecting Up to 20 Slaves More than 20 slave 372 units may be controlled using an external relay See Connecting an External Relay to Attach Slaves If some of the slave units are a long distance away from the master a direct connection might give rise to ground loop problems To avoid this use an external relay to isolate the connection between the master and the distant slaves See Connecting an External Relay to Attach Slaves On the front panel of the slave units press NEXT to locate Trigger Input in the LCD menu display Check to see that Force Sense is selected Force Sense is the default setting Select this mode if you only want the 372 to collect data about the highest and lowest ambient SPL in the installation zone s The 372 does not perform any gain control in this mode You can determine the start of the history period or collec tion of data See History later in this section to reset or start the collection of the relative SPL history To view the current SPL readings see Listen Select this mode when you want to
12. 303 for unbalanced outputs e Connecting speaker for sensing and music paging Connecting speaker for either music or paging does not sense Connecting an external relay if maximum amplifier voltage and wattage exceeded Connecting slave 372s Connecting a switch or contact closure to manually force or prevent sensing SYSTEM SETUP e Choose Operating Mode View calibration Status Collect History of highest and lowest SPLs e Set gain level in Listen e Set MIN limit gain e Set MAX limit gain Specify number of samples Averaging Time Specify Gain Sense Ratio Set Threshold e Specify time for Force Sense Time Enable AGC Specify type of Trigger Input Lock or Unlock Setup CALIBRATION e Equating ambient noise level to 0 db Unity gain Bold face indicates menu name in LCD display Symetrix 372 SPL Computer User s Guide Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing Symetrix FROM TO SPEAKER SENSE LINE OUTPUT LINE INPUT RIGHT LEFT RIGHT LEFT WE E gt mu aota hot INPUT A
13. AY th LINE OUTPUT LINE INPUT RIGHT LEFT RIGHT LEFT ht ho tlh Symetrix OF CS RE Ga OR PS 3E CE 205 power SUPPLY ONLY To connect slave 372 units in remote locations from the master unit External Relay Pack If some of the slave units are a long distance away from the master a direct connection might give rise to ground loop problems To avoid this use an external relay to isolate the connection between the master and the distant slaves Slaved Groups 1 2 3 4 th Sen rh Sen rh Sen rh Sen IMPORTANT ee Please see notes on previous page regarding internal jumper configura tion of the master 372 TO SPEAKER FROM AMP leases SENSE TRIGGI EXT RELAY LINE OUTPUT LINE INPUT RIGHT LEFT RIGHT LEFT h th th th t Slave Group 2 Slave Group 1 Connect a cable from TRIGGER and Ground terminals of the master unit to the External Relay control and Ground terminals on the rear panel of the external relay Connect cables from the external relay outputs to the TRIGGER and Ground terminals of each slave unit in parallel From the front panel of t
14. Oper ating Mode Listen MONITOR Adjusts the volume level at the headphone jack GAIN 3 position switch adjusts the sensitiv ity of the sensing circuitry to accom modate different conditions Set the gain level while in the Listen mode For more information see Description of Menu Features Operating Mode Listen Note Once the 372 has been set up do not change the AMBIENT SENSE GAIN position 14 Symetrix 372 SPL Computer User s Guide System Setup Overview of Front Panel How System Setup Works Description of Menu Features How System Setup Works Use the two push buttons NEXT and EXIT with the parameter adjustment knob ADJUST to gain access to menu setup options in the LCD display 1 Press NEXT to enter the setup mode 2 Rotate ADJUST to select a specific value or choice 3 Press NEXT again to gain access to another menu option Subse quent presses of Next change menu options 4 Press EXIT to end the setup process save any changes made and return the unit to normal operation or Allow 30 seconds of inactivity after which the unit returns to normal operation Does not apply while using the Listen feature 5 After setup is complete calibrate the unit See the section Calibrat ing the 372 REQUIRED RECOMMENDED OPTIONAL MENU FEATURE IN LCD DISPLAY Choose Operating Mode View calibration Status Collect History of highest and low
15. T LEFT RIGHT LEFT connection on the rear panel you Dess tn must also choose Trigger Input in NUT STE the LCD menu display to enable either So SI HE gHHHHHHHHHHHH a force sense or prevent sense event Prevent Sense is useful in the Music mode during voice announcements in conjunction with an external contact closure In Music mode the 372 has no other way to know if an announce ment is happening An example of an external contact closure might be a spare set of contacts on a push to talk micro phone The 372 is prevented from sensing the ambient room level whenever these contacts are pressed closed Otherwise a timed sense event might cut off the announcer when he she is speaking To Force a Sense Event Connect a momentary contact closure between the TRIGGER and Ground terminals Push Button Switch From the front panel of the slave 372 LCD menu display Press NEXT to gain access to Trigger Input Check to see that Force Sense is selected Force Sense is the default setting For additional information see in the section System Setup Description of Menu Features Trigger Input To Prevent a Sense Event Connect a normally open set of switch or relay contacts between the TRIGGER and Ground terminals From the front panel of the slave 372 LCD menu display Press NEXT to gain access t
16. ain service If inside the USA Symetrix will perform in warranty or out of warranty service on any product it has manufactured for a period of five years from date of manufacture If you reside in the USA then proceed as follows In Warranty Repairs Repairs made in warranty will cost you only one way freight charges We ll prepay the return surface freight Of course if the repair is due to operator error parts and labor will be charged If there are charges for the repair costs you will pay for the return freight All charges will be COD unless you have made other arrange ments prepaid Visa or Mastercard For more information see the section Warranty Out of Warranty Repairs If the warranty period has passed you ll be billed for all necessary parts labor packaging materials and freight charges Symetrix 372 SPL Computer User s Guide Service To Get Your 372 Unit Repaired US customers only Call Customer Service Department for a return authorization RA number 425 778 7728 Monday through Friday 8 00 am 4 30 pm Pacific Time Have your serial number ready to give to the customer service representative Pack the unit in its original packaging materials Include your name address daytime telephone number and a brief statement of the problem Write the RA number on the outside of the box Ship the unit to Symetrix freight prepaid We do not accept freight collect shipments Symetrix I
17. an external trigger source or contact closure connected to TRIGGER on the rear panel See Connecting a Push Button Switch to Force or Prevent a Sense Event AGC Enable or Performs simple AGC on the input signal s Disable In Music mode this action consists of low ratio expansion for signal levels below 0 dBu and moderate ratio compres sion for signal levels above 0 dBu This can be useful in reducing the dynamic range of signal sources such as CD players In Page mode this action performs over threshold compression at 3 1 ratio for signals over 0 dBu as referred to the input This can be useful in keeping the sound system out of clipping or for reducing the surprise factor caused by a loud talker REQUIRED RECOMMENDED OPTIONAL 20 Symetrix 372 SPL Computer User s Guide System Setup Overview of Front Panel How System Setup Works Description of Menu Features Description of Menu Features continues ROTATE ADJUST TO SELECT VALUE OR PRESS NEXT TO SELECT MENU FEATURE CHOICE DESCRIPTION Trigger Input Force Sense Prevent Sense Not Used You can manually prevent sensing or manually control sensing by using this feature in conjunction with the hardware connection TRIGGER on the rear panel Forces a sense period when the program material is too dense to contain sufficient gaps for silence sensing Operates independently of Gap Threshold On the rear panel connect a momentary contact cl
18. ap Threshold level You can override the Gap Threshold level by manually controlling sensing See in Description of Menu Features Trigger Input Force Sense in the section System Setup 2 In Page mode whenever the program audio is above the Gap Threshold level 3 In Page mode for about 20 seconds after any program signal above the Gap Threshold level has disappeared 4 In any mode for about 4 seconds after the last sample was taken 5 any mode as long as the TRIGGER input is grounded if Prevent Sense has been selected for Trigger Input in the LCD menu display 6 In Bypass mode 23 Signal Flow Diagram Symetrix 372 SPL Computer User s Guide 40193130 SINH 110 Qq39NY 1V8 1H9IH 0 imm AV1dSIG G91 YOLVNNALLV 3 18VHOLIMS HOLINON 3SN3S WOO Tar t 110 Qq3oNV 1V8 1331 rz LILI 4 Aulifioulo fido LIg 8 alle el ie aa uaxxv3adS div OL 40193130 SINY OOO AV134 IWNYALX3 DEQ a0 1d aSNaS 1snrav O Lee 3ivugnvo O A 1X3 NAW O A 1X3N NNIN CITE NI ann y 1HOIH OON NI NN DOS aaoNviva 7 1491 24 Symetrix 372 SPL Computer User s Guide Input and Output Connector Wiring METHOD CONNECTOR CHANNEL Balanced Terminal Strip Balanced Female XLR Pin 1 Not Connected Pin 2 High Pin 3 Low Con
19. ation Do not operate this equipment under any of the following conditions explosive atmospheres in wet locations in inclement weather improper or unknown AC mains voltage or if improperly fused Do not install near any heat source such as radiators heat registers stoves or other apparatus including amplifiers that produce heat Unplug this apparatus during lightning storms or when unused for long periods of time Stay Out of the Box To avoid personal injury or worse do not remove the product covers or panels Do not operate the product without the covers and panels properly installed Only use accessories specified by the manufacturer Clean only with a damp cloth User serviceable parts There are no user serviceable parts inside the 372 In case of failure refer all servicing to the factory Servicing is required when the 372 has been damaged in any way such as when a power supply cord or plug is damaged liquid has been spilled or objects have fallen into the apparatus the apparatus has been exposed to rain or moisture does not operate normally or has been dropped Equipment Markings CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN TO REDUCE THE RISK OF FIRE OR WARNING ELECTRIC sHock NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE RISQUE DE CHOC ELECTRIQUE AVIS NE PAS OUVRIR SEE OWNERS MANUAL VOIR CAHIER D INSTRUCTIONS No user serviceable parts inside Refer servicing to qualified
20. de Operator Safety Summary Equipment Markings What Ships in the Box Getting Help The 372 unit If you have questions beyond the scope of this guide contact our Customer Service Department in the following ways One PS 3 or PS 3E export version power supply T US customers 425 778 7728 International customers 425 778 7728 This user s guide 8 00 am to 4 30 pm Monday through Friday Pacific Time F 425 778 7727 tech symetrixaudio com www symetrixaudio com Optional Rackmount Accessories MODEL ITEM DESCRIPTION RM 3 19 Rackmount Tray 1U shelf FP 3 Filler Panel Covers unused half of rack tray when one 372 unit is mounted PY 3 Y Power Cable Connects a 372 with any other 300 Series product Contact your dealer or Symetrix for purchasing information Notational Conventions in this User Guide Note Identifies information that needs extra emphasis Generally supplies extra information to help you to better use the 372 CAUTION Identifies information that if ignored may cause damage to the 372 or other equipment in your system WARNING Identifies information that if ignored may be hazardous to your health or that of others SMALL CAPS Controls switches or other markings on the chassis of the 372 Bold Face Indicates menu option in the 372 LCD display Symetrix 372 SPL Computer User s Guide Before You Begin What Ships in the Box Getting Help Optional Rackmount Accessories Notational Co
21. de to check the level of the signal while the 372 senses You may need to lower the gain position of the AMBIENT SENSE GAIN switch More information about the gain setting is found in Listen under the section System Setup A common practice in 70V systems is to provide autotransformers or L pads after the line transformer to allow local volume control These controls should not be used with the 372 Allowing any sort of signal level control after the 372 invalidates your calibration settings If you must provide a local control then ensure that the controlled zone is a minor part of the entire system In this controlled zone volume level will not be ideal and sensing should not be used Also it is imperative that every speaker and transformer in the system operate in phase 4 8 and 16 Ohm Systems In these speaker impedance systems the signal levels returned to the 372 are low Use the Listen mode to check the level of the signal while the 372 senses You may need to select the high gain position of the AMBIENT SENSE GAIN switch Symetrix 372 SPL Computer User s Guide Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing 372 Basic Co
22. dealer or sales representative to assume any liability or make any additional warranties or representation regarding this prod uct information on behalf of Symetrix This limited warranty gives the buyer certain rights You may have additional rights provided by applicable law NOTE Some Symetrix products contain embedded software and may also be accompanied by control software intended to be run on a personal computer Said software is specifically excluded from this warranty The total liability of Symetrix on any claim whether in contract tort including negligence or otherwise arising out of con nected with or resulting from the manufacture sale delivery resale repair replacement or use of any product will not exceed the price allocatable to the product or any part thereof which gives rise to the claim In no event will Symetrix be liable for any incidental or consequential damages including but not limited to damage for loss of revenue cost of capital claims of customers for service interruptions or failure to supply and costs and expenses incurred in connection with labor overhead transportation installation or removal of products substitute facilities or supply houses 30 Where to Get Service If outside of the USA If you have determined that your 372 requires repair services and you live outside of the United States please contact your local Symetrix dealer or distributor for instructions on how to obt
23. est SPLs Set gain level in Listen e Set MIN limit gain e Set MAX limit gain Specify Averaging Time Specify Gain Sense Ratio e Set Gap Threshold e Specify time for Force Sense Time Enable AGC Specify type of Trigger Input Lock or Unlock Setup Bold face indicates menu name in LCD display 15 Symetrix 372 SPL Computer User s Guide System Setup Overview of Front Panel How System Setup Works Description of Menu Features Description of Menu Features ROTATE ADJUST TO SELECT VALUE OR DESCRIPTION PRESS NEXT TO SELECT MENU FEATURE CHOICE Operating Mode Music Page REQUIRED RECOMMENDED OPTIONAL This mode considers everything if it were music even though it may contain a mix of music and announcement audio Varies the gain of this program channel to match the ambient noise level How Sampling Works Takes SPL measurements during silent portions in the program material If the 372 doesn t find gaps then it forces a sense period samples for about 0 75 seconds after which it restores the program channel signal How You Can Control Sampling You can force a sense period manually and select the time of the forced event See Trigger Input in this section to enable this feature Can also perform simple AGC on the input signal to improve the consistency of the output level See AGC in this section to enable this feature Select this mode if you are doing paging o
24. he relay Symetrix v fete une wr and the relay must have a back NC Sth tata biased 1N4002 diode connected O e HEHHEHHEHRHH across its coil to absorb the back EMF i from the relay coil The transistor has 60V VCE rating MPSA 06 The 24V version of the Potter amp Brumfield PRD11DGO works well Its DPDT contacts are rated at 30A 10 Symetrix 372 SPL Computer User s Guide Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing Connecting Up to 20 Slaves A master 372 can direct any number of slave 372 units to take an ambient sample You can parallel slave 372 units directly together from the master unit to enable you to sense at the same time in adjacent or multiple installation zones If the slave 372 units are in remote locations use an external relay to connect the slaves to the master unit see Connecting an External Relay to Attach Slaves As many as 20 slave 372 units may be controlled directly from the master 372 MAXIMUM CABLE LENGTH Depends upon the difference in ground potential if any between the individual un
25. he slave 372 LCD menu display Press NEXT to gain access to Operating Mode Rotate ADJUST to select Slave mode Press NEXT to locate Trigger Input Check to see that Force Sense is selected Force Sense is the default setting See Description of Menu Features Operating Mode Slave in the section System Setup for additional information 19 See eee Hee Fe BEBE 12 Symetrix 372 SPL Computer User s Guide Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing Connecting a Push Button Switch to Force or Prevent Sensing You can manually prevent sensing or manually control sensing by using a push button switch In conjunction with the TRIGGER Symetrix FROM AMP TO SPEAKER SENSE LINE OUTPUT LINE INPUT RIGH
26. intervals SLAVE Forces all 372 units in a multi zone system to execute a sense sample at the same time HISTORY Records and displays the lowest and highest SPL readings from when the unit was last reset BYPASS Bypasses the gain control of the SPL controller and the AGC Signal Path Controls mono or stereo signals through Euroblock connectors Programmable Sensing Operation Select the auto sense mode and or the time interval between sense samples Simple Calibration Use step through menus on the front panel LCD Perform calibration under typical installation conditions No waiting for the quietest or noisiest ambient environment AGC Control Enables or disables auto leveling of input signals Ambient Adjustment Choose an adjustment ratio of SPL change vs program level change Sense Signal Monitoring Display numeric reading and relative bargraph of the signal appearing at the sense terminals Listen to sense signal with headphones connected to front panel mono output Gain Controls Set minimum and maximum limits for SPL gain range Gain range is 20 to 30 db Averaging Time Choose integration time of the running average SPL Symetrix 372 SPL Computer User s Guide Checklist of Tasks for Hardware Connections System Setup and Calibration REQUIRED RECOMMENDED OPTIONAL TASK TO DO HARDWARE e Connecting input sources CONNECTIONS e Connecting output sources use Symetrix
27. its IMPORTANT As of 372 hardware revision C an internal jumper J8 has been added which must be in correctly config ured on the master 372 in order to properly drive the slaves On the master 372 remove the top and move the jumper J8 to con nect pins 2 and 3 Pins 1 and 2 are connected at the factory This is the default position and this jumper should only be changed on the mas ter 372 J8 should remain in the fac tory default position on all slaves Moving J8 to connect pins 2 and 3 configures the TRIGGER input connection on the Master 372 to become a Slave Drive OUTPUT This reconfiguration is necessary to pre vent a false sensing problem when multiple zones bleed into each other This new way of configuring the master 372 ensures that all 372 s will sense in sync thus avoiding false sense readings from zone bleed Master 372 SENSE TRIGGER EXT RELAY h LINE OUTPUT LINE INPUT RIGHT LEFT RIGHT LEFT b th sbhb th t Symetrix POWER ae oes TO INPUT 27 lt p53 OR PS 3E 099 POWER SUPPLY ONLY FROM TO SPEAKER Slave 372 SPEAKER em ass SENSE LINE OUTPUT LINE INPUT RIGHT LEFT RIGHT LEFT ho th th Symetrix POWER CONNECT TO SYMETRIX INPUT 27 5 psa OR C 208
28. m the sound system even if the ambient drops to dead silence Set MAX Limit Select value To adjust the highest gain setting that the 372 uses This ensures that the sound system stays out of clipping even if the ambient level exceeds your wildest expectations WB Averaging Time 1 2 4 or 8 To average together the number of samples to make a gain change Select the number of samples you want the 372 to use Longer running averages make the system respond more to the trend of the ambient level rather than the most recent sample Gain Sense Ratio REQUIRED RECOMMENDED OPTIONAL 0 5 1 1 1 1 5 1 or 2 1 Refers to the change in gain of the 372 versus the change in the ambient 0 5 1 changes gain 0 5 dB for every dB change in the ambient This makes the sound system louder in response to increases in the ambient but never tries to out shout the crowd 1 1 matches gain changes to the ambient noise level 1 5 1 changes gain 1 5 dB for every 1 dB increase in the ambient noise level 2 1 changes gain 2 dB for every 1 dB increase in the ambient noise level At high ambient levels the 372 can easily out shout the crowd if the control settings allow it To limit the 372 s ability to out shout the crowd pick a lower maximum gain in Set MAX Limit At lower ambient levels the 372 might let the sound system get lost in the ambient To avoid this choose a higher closer to 0 dB minimum gain in Set
29. nc 6408 216th St SW Mountlake Terrace WA 98043 If You Don t Have Factory Packaging Materials If you send us your product in substandard packaging we will charge you for factory shipping materials If you don t have the factory packaging materials do the following 1 Select an oversized carton 2 Wrap the unit in a plastic bag and surround it with bubble wrap 3 the box full of Styrofoam peanuts Be sure there is enough clearance in the carton to protect the rack ears We will return the unit in Symetrix packaging 31 Symetrix 372 SPL Computer User s Guide Declaration of Conformity We Symetrix Inc 6408 216th ST SW Mountlake Terrace Washington USA declare under our sole responsibility that the product 372 SPL Computer to which this declaration relates is in conformity with the following standards EN 55103 1 Electromagnetic Compatibility Generic Emission Standard Part 1 Residential Commercial and Light Industry EN 55103 2 Electromagnetic Compatibility Product Family Standard for Audio Video and Entertainment Lighting Control Apparatus for Professional Use Part 2 Immunity PS 3E power supply complies with this code EN 60065 Safety Requirements for Mains Operated Electronic and Related Apparatus for Household and Similar General Use The technical construction file is maintained at Symetrix Inc 6408 216th St SW Mountlake Terrace WA 98043 USA The authorized represen
30. nector Shield Not Connected Balanced TRS Plug Tip High Ring Low Sleeve Shield Unbalanced TS Plug Tip High Sleeve Low Shield Unbalanced RCA Plug Tip High Sleeve Low Cable Shield Not Connected Balanced Male XLR Pin 1 Circuit Ground Pin 2 High Pin 3 Low Unbalanced TS Plug Tip High Sleeve Shield Wire Low Not Connected v a mr TIP i UE SLEEVE SLEEVE h mim qua h Ree r dg SLEEVE 25 Input Input Input Input Input Output Output SYMPTOM Symetrix 372 SPL Computer User s Guide Troubleshooting PROBABLE CAUSE WHAT TO DO No output signal Check cables and connections to see if Inputs are driving outputs and outputs are driving inputs There is a signal coming from the source and that it is getting to the 372 The signal chain after the 372 is functioning Check if the LCD display is on and unit is plugged in Unit will not calibrate Check that input levels are normal In Listen mode use headphones to hear what the 372 reads Set position of AMBIENT SENSE GAIN switch between 40 and 0 dB Check sensing speaker connec
31. nnection Signal I O Connections These connectors are designed for use with bare wire Do not tin strand wires before inserting them into the connectors If using unbalanced connections see wiring diagram in the section Input and Output Connector Wiring Note Feeding unbalanced inputs directly from balanced outputs is not recommended due to the possibility of ground loops An option is to use the Symetrix 303 isolation transformer to break the ground connection and eliminate the ground loop 1 Connect your line level source to the rear panel input connectors These connectors may be driven from a balanced or unbalanced source When using an unbal anced source connect the output minus terminal to ground either at the source or at the 372 2 Connect the outputs as required These connectors deliver a differential balanced output signal For unbalanced use use the positive line output terminals and the ground terminals Ignore float the minus output terminals Amplifier and Speaker Connections 3 Connect your amplifier and speakers to the barrier strip connectors The speaker and amplifier connec tions are earth free floating The 372 treats the speaker connections after its sensing relay as if they were a balanced line Do not ground either side of the speaker line It is OK if the one side of the amplifier output is grounded Connect all speakers used for sensing and either music or paging to this
32. nternally pulled to the 5V supply by way of a 20k ohm resistor From this connection attach slave 372 units to the master 372 Symetrix 372 SPL Computer User s Guide Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing CONNECTION CONNECTOR TYPE WHAT IT DOES LINE OUTPUT Euroblock terminals These connectors deliver a differential balanced output at 200 ohm source impedance For unbalanced use use the positive line output terminals and the ground terminals Ignore float the minus output terminals The output stage is a pair of opamps with the plus and minus output terminals at 180 antiphase with each other It emulates a grounded center tap transformer The series build out resistors are 100 ohms in each leg For wiring diagram see the section Input and Output Connector Wiring LINE INPUT Euroblock terminals Balanced input for the 372 20k ohm balanced bridging For unbalanced sources connect the minus input terminal to the source ground at the source Note Feeding unbalanced inputs directly from balanced outputs is not recommended due to the possibility of ground loops You may want to use the Symetrix 303 isolati
33. nventions in this User Guide Operator Safety Summary Equipment Markings Operator Safety Summary Follow all warnings and instructions Install in accordance with the manufacturer s instructions Power Source This product is intended to operate from a Symetrix PS 3 or PS 3E power supply Grounding The chassis of this product is grounded through the grounding conduc tor of the PS 3 or PS 3E power cord To avoid electric shock plug the power cord into a properly wired receptacle before making any connections to the product A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation Do not defeat the safety purpose of the grounding plug The grounding plug has two blades and a third grounding prong The third prong is provided for your safety When the provided plug does not fit your outlet consult an electrician for replacement of the obsolete outlet Danger from Loss of Ground If the protective ground connection is lost all accessible conductive parts including knobs and controls that may appear to be insulated can render an electric shock Proper Power Cord Use only the power cord and connector specified for the product and your operating locale Use only a cord that is in good condition Protect the power cord from being walked on or pinched particularly at the plug convenience receptacle and the point where the cord exits from the apparatus Operating Loc
34. o Trigger Input Rotate ADJUST to select Prevent Sense For additional information see in the section System Setup Description of Menu Features Trigger Input 13 Symetrix 372 SPL Computer User s Guide System Setup Overview of Front Panel How System Setup Works Description of Menu Features SETUP AMBIENT SENSE MENU ADJUST CAL MONITOR GAIN NEXT EXIT s COMPUTER e O o 9 ina Overview of Front Panel CONTROL CONTROL TYPE WHAT IT DOES SETUP LCD menu display Two line display shows levels and settings of selected menu feature NEXT From normal operation the first press enters the setup mode subsequent presses step through the setup process EXIT Exits the setup mode The unit reverts to normal operation ADJUST Rotary control used in setup mode for parameter setting CAL Press to have the 372 read the current ambient level and equate this reading to 0 db Unity gain Displays the relative ambient reading which it considers as normal CAL is only active in normal operating mode and when setup is unlocked AMBIENT SENSE Headphone jack 1 4 inch TRS jack suitable for head phone impedances of 60 ohms or higher stereo or mono Enables listening to the output of the sensing system when 372 is in Listen mode Helpful for troubleshooting or for figuring out what the 372 is listening to For more information see Description of Menu Features
35. on transformer to break the ground connection and eliminate the ground loop With unbalanced sources it is preferable to carry the low side of the input all the way back to the ground connection of the source For wiring diagram see the section Input and Output Connector Wiring Symetrix 372 SPL Computer User s Guide Making Hardware Connections Overview of Rear Panel Connectors and Connections Sensing Speaker Considerations 372 Basic Connection Connecting an External Relay to Drive Amplifiers Larger than 200W Connecting Up to 20 Slaves Connecting an External Relay to Attach Slaves Connecting a Push Button Switch to Force or Prevent Sensing Sensing Speaker Considerations Speaker Location If a sensing speaker is located near a localized noise source that is not typical for the ambient noise level of the controlled zone the 372 deter mines that the zone is noiser than it really is For example the noise from a large machine of some sort or maybe a kids play area or a video game The solution is to have the speakers that are near the noise source driven directly from the amplifier so that they are not used for sensing 70V Systems In a 70V system the signal level returned by the speakers when the 372 is sensing is higher because of the step up action of the line trans formers With highly efficient speak ers this may present the problem of overloading the sense input of the 372 Use the Listen mo
36. ons there shall be connections provided for a sense trigger input and an open collector sense trigger output A front panel power indicator shall be provided A liquid crystal display shall be provided to communicate operat ing parameters and setup information with the user The ALC shall occupy half of the width of one rack space and shall be housed in a metal enclosure It shall use an external safety agency approved power supply The Ambient Level Controller shall be the Symetrix model 372 SPL Computer 29 Symetrix 372 SPL Computer User s Guide Warranty Symetrix Inc expressly warrants that the product will be free from defects in material and workmanship for eighteen 18 months from the date the product is shipped from the factory Symetrix s obligations under this warranty will be limited to repairing or replacing at Symetrix s option the part or parts of the product which prove defective in material or workman ship within eighteen 18 months from the date the product is shipped from the factory provided that the Buyer gives Syme trix prompt notice of any defect or failure and satisfactory proof thereof Products may be returned by Buyer only after a Return Authorization number RA has been obtained from Symetrix Buyer will prepay all freight charges to return the product to the Symetrix factory Symetrix reserves the right to inspect any products which may be the subject of any warranty claim before repair or
37. osure between the TRIGGER and Ground terminals to initiate an ambient level sense event See Connecting a Push Button Switch to Force or Prevent Sensing Enables slave 372s connected to a master 372 to sense at the same time in adjacent or multiple zones See Slave mode in this section and in the section Making Hardware Connections see Connecting Up to 20 Slaves Useful in Music mode during voice announcements in conjunction with an external contact closure In Music mode the 372 has no other way to know if an announce ment is happening Connect to the TRIGGER input a normally open set of switch or relay contacts between the TRIGGER and Ground terminals on the rear panel An example of this might be a spare set of contacts on a push to talk microphone Whenever these contacts are pressed closed the 372 is prevented from sensing the ambient room level Other wise a timed sense event might cut off the announcer when he she is speaking See Connecting a Push Button Switch to Force or Prevent Sensing Disables the trigger pin Setup Unlocked Unlock or lock REQUIRED RECOMMENDED OPTIONAL Choose to protect front panel LCD menu settings from being altered To lock press and hold CAL while rotating ADJUST Once it s locked pressing NEXT shows the current settings Any attempt to alter settings results in the display of the message Setup is Locked To unlock press NEXT until the display reads
38. r announcement audio only Varies the gain of the program channel to match the ambient noise level How Sampling Works The presence of audio in the program channel prevents sampling from taking place Sampling stays locked out until the program channel has remained silent for at least 20 seconds In the rare event that a page or announcement begins while sampling is taking place Samples for about 0 75 seconds the current sense cycle period will complete and then further sampling is prevented How You Can Control Sampling If your application cannot tolerate paging interuptions you can force sensing to occur after a page announcement See Force Sense Time in this section to enable this feature Can perform simple AGC on over threshold compression on the paging signal at 3 1 ratio on signals above 0 dBu defeatable See AGC in this section to enable this feature 16 Symetrix 372 SPL Computer User s Guide System Setup Overview of Front Panel How System Setup Works Description of Menu Features Description of Menu Features continues PRESS NEXT TO SELECT MENU FEATURE ROTATE ADJUST TO SELECT VALUE OR CHOICE DESCRIPTION Operating Mode continues REQUIRED RECOMMENDED OPTIONAL Slave History Bypass Select this mode if you want to designate the 372 unit as a slave Slave units connected to a master 372 unit enable you to sense at the same time in adjacent or multiple installation
39. service personnel Il ne se trouve a l interieur aucune piece pourvant entre repar e l usager S adresser a un reparateur comp tent The lightning flash with arrowhead symbol within an equilateral triangle is intended to alert the user of the presence of uninsulated dangerous voltage within the product s enclosure that may be of sufficient magnitude to constitute a risk of electric shock to persons The exclamation point within an equilateral triangle is intended to alert the user of the presence of important operating and maintenance servicing instructions in the literature accompanying the product i e this user s guide CAUTION To prevent electric shock do not use the polarized plug supplied with the unit with any extension cord receptacle or other outlet unless the blades can be fully inserted Symetrix 372 SPL Computer User s Guide Features of the 372 Uses Speakers for Noise Sensing In less than 1 second the Symetrix 372 temporarily opens up the amplifier connection and routes the loudspeakers to a preamplifier for the purpose of measuring changes in the ambient noise level Samples during absence of page and or music audio or at preset intervals Headphone Monitoring Monitor the sense signal using a separate front panel headphone output 5 Operating Modes MUSIC Music only or music page Use Gap and or Force Sense Time PAGE Only paging and annoucement audio Use Force Sense Time at preset
40. tative located within the European Community is World Marketing Associates P O Box 100 St Austell Cornwall PL26 6YU UK Date of issue June 30 2000 Place of issue Mountlake Terrace Washington USA Authorized signature Dane Butcher President 32 301 302 303 304 305 306 307 308 372 402 420 421M 422 440 450 501 501 01 506E 527E 528E 531E 532E 533E 551E 552E 562E 565E 571 571S 572 581E 606 610 628 9022 RC 1 RC 2 RC 610 Low Distortion Compressor Limiter Dual Microphone Preamplifier Interface Amplifier Headphone Amplifier Distribution Amplifier 1x4 Preamp Ducker Dual Isolation Transformer VCA Volume Control Loudness EQ SPL Computer Dual Output Delay Stereo Power Amplifier AGC Leveler Stereo AGC Leveler Foreground Audio Controller Dual Zone Priority Mixer Peak RMS Compressor Limiter Peak RMS Compressor Limiter Headphone Amplifier Voice Processor Voice Processor Graphic Equalizer Graphic Equalizer Graphic Equalizer 5 Band Parametric EQ Dual 5 Band Parametric EQ Windowing Expander Gate Dual Compressor Limiter Expander SPL Computer SPL Computer Slave SPL Computer Distribution Amplifier 4x4 Delay F x Machine Broadcast Audio Delay Digital Voice Processor 2x2 DSP Engine 628 Remote Control 440 Remote Control Remote Control Symetrix www symetrixaudio com
41. ten REQUIRED RECOMMENDED OPTIONAL Select Listen in order to set the gain level There is a 2 second delay prior to entering this function The 372 switches the system into Listen mode silencing the speakers and using them as microphones to read the ambient sound level The relative SPL reading then displays in numeric form and also as a bargraph Adjust the AMBIENT SENSE GAIN switch on the front panel until the indicated level is higher than at least 40 dB but no more than 0 dB This setting range allows the 372 to have enough valid information to control the system gain Note Once the 372 has been set up the AMBIENT SENSE GAIN switch position should never be changed In this mode you can plug in headphones to listen to the ambient sound the 372 reads Adjust the volume of the headphones by rotating MONITOR The headphone is a helpful troubleshooting tool for identi fying noise sources that may be misdirecting the 372 or hum and noise picked up in the speaker wiring that may be causing sense errors 18 Symetrix 372 SPL Computer User s Guide System Setup Overview of Front Panel How System Setup Works Description of Menu Features Description of Menu Features continues PRESS NEXT TO SELECT MENU FEATURE ROTATE ADJUST TO SELECT VALUE OR CHOICE DESCRIPTION Set MIN Limit Select value To adjust the lowest gain setting that the 372 uses This ensures a known minimum level fro
42. the ambient noise level These parameters are minimum and maximum gain through the device silence sensing threshold noise sensing protocol gain sense ratio program AGC or compression and averaging time In addition the Symetrix 372 SPL Computer User s Guide Architects and Engineers Specifications ALC shall provide music or paging signal modes bypass mode slave mode for linking multiple units and a history mode that collects and displays ambient noise history from the controlled space The ALC shall provide two indepen dent line level balanced inputs and outputs that control two audio signals The maximum input level shall be 20 dBu and the maximum output level shall be 26 dBu 22 dBm into 600 ohms balanced The balanced input impedance shall be 20 000 ohms and the output source impedance shall be 200 ohms bal anced 100 ohms unbalanced The gain control range shall be 30 dB to 20 dB The frequency response shall be 20 Hz to 20 kHz 0 1 dB with THD N less than 0 25 at 4 dBu over the same range of frequencies The output noise of the device shall be less than 95 dBu 20 kHz noise bandwidth unity gain The input and output configuration shall be active balanced The speaker switching relay contacts shall be rated at 8A Screw terminals shall be used for all connections except for the speaker connections which shall utilize a barrier style terminal strip In addi tion to the audio input outut connec ti
43. tions Music always plays too loud Check levels in Set MIN Limit and or Set MAX Limit Unit seems to have no effect Check the ratio setting in the LCD menu display for Gain Sense Ratio At 0 5 1 the gain changes are very subtle Choose a larger value for more change Check if level is set too low in Set MAX Limit Unit never senses even during silence Check if Gap Threshold is set too low Check if Bypass mode or Slave mode is selected in Operation Mode Change mode to Music or Page Unit loses the beginnings of paging messages Gap Threshold set too high Select Sense After Page Unit does not accurately adjust system as ambient noise changes Hum induced in speaker wiring Check if speaker wiring is routed adjacent to AC wiring In Listen mode use headphones to check ambient noise level Check if speaker is mounted near continuous noise source Check that all speakers are operating in phase Note The accuracy of the 372 is only as good as the quality of your speakers Unit senses during paging Gap Threshold set too high choose a lower value Hum or buzz in output Check input connector wiring Check for a ground loop problem Inspect related system equipment grounding to see that all system components are on the same AC ground 26 Symetrix 372 SPL Computer User s Guide Troubleshooting SYMPTOM PROBABLE CAUSE Distortion Check input signal for distortion Check
44. y Euroblock Headphone 1 4 in TRS will drive mono or stereo headphones Internal Relay double pole contacts rated 8A maximum Physical Size H x W xD 1 2 rack unit 1 75 in x 8 5 in x 6 5 in 4 445 cm x 21 59 cm x 15 875 cm Shipping Weight 4 5 Ibs Electrical Power Requirements 10W maximum Symetrix PS 3 or PS 3E only PS 3 115V 60 Hz AC nominal PS 3E 230V 50 Hz to 60 Hz AC nominal Note In the interest of continuous product improvement Symetrix Inc reserves the right to alter change or modify these specifications without prior notice 28 The Ambient Level Controller ALC shall control the output level of the sound system in response to the observed acoustical noise level within the controlled space during system operation These measurements shall be made during silent portions of the program material Provision shall be made to alter the noise sensing protocol to make the noise level measurement under timer or external control and to accomodate musical or paging program signals The ALC shall utilize the loudspeakers of a sound system as microphones to sense the ambient noise level Provision shall be made for the user to monitor the audio signal used by the ambient sense system by using headphones The ALC shall be capable of operating from sound systems using direct loudspeaker drive or constant voltage distribution The ALC shall provide user adjustable parameters to alter the way that it responds to changes in
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