Transmit Audio Circuits
Theory of Operation 6.3-9
4.4 Option Board Audio (GM950i only)
The audio coming from the microphone (J0101-16) or the external microphone (J0400-2) is routed
through Op-amp buffer U0106-2 (GM950i only) to the option board connector J0103-3. After option
board processing the signal emerges at J0103-1. The source resistor of the option board output and
C0145, the amplifier inside the AFIC (U0103-9,10) and gain setting resistor R0147 pre-emphasise
the signal. Inside the AFIC the signal follows a path identical to conventional transmit audio. The
modulation signal emerges from the AFIC at J0103-19/20. Both signals are weighted by resistors
R0181, R0182 and add up to signal MOD IN.
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