12-11. DIGITAL DATA TRANSMIT SIGNAL PATH. Continued
TF data is input to the RCU on AUD/DATA pin D (AT/DDCO) and is switched to the summing network in the ICOM
data I/O module when DGTL CLK OUT EN-N is a logic 1. DGTL CLK OUT EN-N is a logic 1 when the TF data rate is
selected. The TF data follows the transmit analog path through the ICOM data I/O module and is output on the LIM
ANLG DATA line. The TF data is converted to logic 0/1 levels by a limiter prior to output. The LIM ANLG DATA is
input to the ICOM control module, where the logic 0/1 1200 Hz and 2400 Hz signals are FSK demodulated. The
FSK demodulator outputs a logic 1 when 1200 Hz is input and outputs a logic 0 when 2400 Hz is input, The output
of the FSK demodulator is routed to the data rate adapter and is handled by the rest of the RCU as low speed
12-12. SPEAKER OPERATION.
When the SPKR switch is in the position, +13 V dc is routed to a shunt regulator in the DC power filter. See
figure FO-24. The shunt regulator outputs two voltages (SPKR AMP +13 V dc and SPKR AMP VCC/2) used by the
speaker amplifier module. Audio input to the speaker amplifier is taken from VOL POT (VAR) output of the VOL
switch. in the speaker amplifier, the audio is buffered and routed to a switch. The switch is disabled when the RCU
is transmitting, when the RCU is receiving digital or analog data, and when the WHSP mode is being used.
Otherwise, the switch is enabled. The switched receive audio is input to the speaker amplifier which outputs SPKR
(+) and SPKR (-), SPKR (+) and SPKR (-) are input to the DC power filter and are transformer-coupled to the
SPKR (+) OUT and SPKR (-) OUT lines which are routed to the front panel SPKR connector.
12-13. PRIMARY CONTROL SIGNALS.
The primary control signals originate at the front panel. They direct the operation of the RCU. The connectors,
switches, controls, and circuitry on the front panel are connected to the parent board through three connectors.
They are the front panel switches connector (J1), the display connector (J2), and the audio/data connector
(J3). See figure FO-25.
The function of the RCU is controlled by the FCTN switch. When it is set to primary power is removed from
the RCU. The switch position is checked by the control module. If the switch is set to TST, SQ OFF, RXMT, ICM,
LD, or the corresponding line to the control module is set to logic 1 by the switch. If none of these lines
are at logic 1, the control module sets the RCU for SQ ON operation.
Primary power (PRI 13 V dc) for the RCU is also routed through the FCTN switch. Primary power is provided at pin
F of the system connector (P1). The 13 V dc will be applied to the SWITCHED 13 V dc line when the FCTN switch is
at any position other than . The SWITCHED 13 V dc provides the input voltage for the power
supply (19A1 pins B and C). If the FCTN switch is set to the 13 V dc will be applied to the STBY 13 V dc
line. Both SWITCHED 13 V dc and STBY 13 V dc lines are routed to the ICOM power supply where they are used to
power the V HOLD line.
Two voltages are available to retain the fill information in the control module. They are V BATT and V HOLD. V
BATT is provided by the holding battery and is routed through the FCTN switch. V HOLD is provided by the ICOM
power supply. It is derived from the primary input voltage. If both are present, V HOLD will be used instead of V
BATT. Both are turned off when the FCTN switch is set to