EU FM transmissions carrying RDS data. VSM goes to an ADC on the
PW338 and provides a signal strength indication. The AM/FM module gives
an analogue output which is buffered through a ground balancing circuit
(IC302 NJM2114 op amp).
IR from the front panel comes onto this board from L126 and goes through a
re-modulator circuit (IC200 LMC555) as it has been demodulated on the front
panel. This signal, Z1 remod, goes through SKT200 such that inserting a plug
into SKT200 will stop this signal (to prevent conflicting signals if a Zone 1
external IR sensor is used) from going to LED200 and then being
demodulated by RX200.
Zone 2 (SKT102) & Zone 3 (SKT103) IR inputs drive LED201 & LED202
which are demodulated by RX201 & RX202.
Zone 1, Zone 2 & Zone 3 are also multiplexed together to give IR Out through
TR207 & SKT104.
The ground balancing circuit uses +5V_1 from L123 and generates -5V from
IC303 (SP6661EN charge pump). The AM/FM module uses +9V_FM,
generated with REG202 (LM317) from +15V (from L123). +12V_IR is
generated from +15V (L123) using REG200 (LM7812) and runs the IR output
& 12V triggers. +5V_STBY (L123) generates +3V3_STBY with REG201
(LM1117) – used by IC102 (MAX3232) so the RS232 comms are still
available in standby. +3V3_D is generated from +5V_1 (L123) with REG203
and is used by the DAB module.
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