S-COM 6K Owner's Manual page 19

8. RECEIVER #2 (CONTROL/LINK RECEIVER) AUDIO
If you decide to add a second receiver, the controller will require audio from it. RX2 Audio should
be connected to pin 12 of the controller's J2 connector.
The controller's RX2 Audio input circuitry is designed exactly like the RX1 Audio input. The op amp
in this case is U22C, and the level adjust pot is R76. The feedback resistor labeled R27 (100k) has
a circled letter "B" near one lead on the PC board. You may cut this lead and lift the resistor to
increase the gain by a factor of 3. If you are driving the RX2 audio input with pre-emphasized
audio, replace C48 (47 pF) with a 0.01 uF if factory gain is used. Replace C48 with a 0.0047 uF if
the increased gain modification has been done. You may wish to refer back to the "RECEIVER #1
AUDIO" section of this manual for a discussion of the hardware design of the audio input circuit.
After you have completed the Receiver #2 audio interfacing, power up both the receiver and the
controller. Check the audio level at pin 8 of U22C. The level should be about 700 mV rms (2 V p-p)
of audio when the receiver is fed a fully-deviated 1 kHz sine wave tone from a service monitor.
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6K V1.02 03-16-91