HERE IS A MODIFICATION THAT IS REQUESTED ON ALMOST A DAILY BASIS AT 
    OUR SERVICE SHOP.  IT'S A SIMPLE SIDETONE CIRCUIT REFERRED TO IN MOST
    TECH CIRCLES AS TALKBACK.  IN ALL RADIOS UTILIZING TRANSFORMER DE-
    RIVED AUDIO, A SMALL AMOUNT OF RESISTANCE IS COUPLED FROM THE EXTER-
    NAL SPEAKER CIRCUIT (HOT) TO DC GROUND.  150 OHMS SEEMS TO BE AN EX-
    CELLENT VALUE WHEN THE TRANSCEIVER IS USED WITH EITHER THE STOCK MIC.
    OR THE TELEX RK-56/B NOISE CANCELLING MICROPHONE.  CONTRARY TO POPU-
    LAR BELIEF, THE PURPOSE OF THIS CIRCUIT IS TWOFOLD:  FIRST OF ALL, IT
    SHOULD PROVIDE JUST ENOUGH OUTPUT LEVEL (SIMILIAR TO SIDETONE IN AN
    ORDINARY TELEPHONE) SO THAT THE RADIO OPERATOR WILL KNOW IF THE MIC-
    ROPHONE IS WORKING PROPERLY.  (TRANSMIT, RECEIVE AND AUDIO SWITCHING
    FUNCTIONS CAN BE MONITORED IN THIS MANNER)  SECONDLY, IT CAN ALSO BE
    USED TO ADJUST TIME AND DELAY CONTROLS ON THE INFAMOUS CONNEX EB-3
    ECHO BOARD, WHICH WILL BE DISCUSSED AT SOME LENGTH IN ANOTHER FILE IN
    THIS DIRECTORY, SO I WILL NOT GO INTO THAT FOR THE PRESENT.  THE 
    COMPONENT VALUE LISTED EARLIER WORKS EXTREMELY WELL WHEN SAY, THE
    COBRA 29/LTD/CLASSIC/WX/ST IS PROPERLY TUNED AND PRODUCING THE USUAL
    + OR - 25 WATTS/TX @ - 100% MODULATION LEVELS, AND WITH THE DYNAMIKE
    GAIN FULLY CLOCKWISE THERE SHOULD BE NO FEEDBACK BETWEEN THE SPEAKER
    AND THE MIC. AT NORMAL IN CAB DISTANCES.  THIS 150 OHM, 1/4 WATT
    RESISTOR WILL WORK IN ALMOST 90% OF ALL THE RADIOS ON THE MARKET,
    FITTING THE REQUIREMENTS MENTIONED EARLIER.  (TRANSFORMER DERIVED 
    AUDIO)  WITH VALUES SMALLER THAN 150 OHMS YOU WILL NOT BE ABLE TO 
    TURN THE MIC GAIN UP ALL THE WAY WITHOUT EXPERIENCING HIGH LEVELS
    OF AUDIO FEEDBACK.  NOTE: IF YOU ARE UNABLE TO RUN THE MIC GAIN AT
    THE FULL CLOCKWISE POSITION, (OR CLOSE TO IT) THE TRANSMITTER WILL
    NOT BE ABLE TO PRODUCE MAXIMUM OUTPUT.



    LOOK FOR MORE "TALKBACK" RELATED INFORMATION IN A FILE CALLED:

    CONNEX.TXT...................................IN THE CURRENT DIRECTORY