Icom IC-2GA Service Manual page 14

(9) T5/R5 SWITCHING CIRCUIT (MAIN UNIT)
When the PTT switch (S205) is pushed, Q216 is turned on.
The collector of Q215 outputs a "LOW" signal to the CPU
(IC503, pin 44). Using the "LOW" signal, the CPU sends
TRANSMIT data to IC202. 1C202 (pin 13) outputs a "HIGH"
signal to ІС203С (рт 8) and IC203A (pins 12 and 13),
controlling IC203C (pin 10) — shutting off R+5.
IC203A (pin 11) outputs a "LOW" signal to ІС203В (ріп 2),
controlling the base of 0209 — turning on T4 5.
T5/R5 SWITCHING CIRCUIT
Releasing the PTT switch turns off Q216. The collector of
Q215 outputs a "HIGH" signal which causes the CPU to
send RECEIVE data to 1С202. 1C202 (pin 13) outputs а
"LOW" signal to ІС203С (ріп 8) and IC203A (pins 12 and
13), controlling IC203C (pin 10) — turning on R+5S.
1C203A (pin 11) outputs a "HIGH" signal to IC203B (pin 2)
controlling the base of Q209 — turning off T+5.
+55
0213, 0214
0211, 0212
LOW POWER CHARGE PUMP
DESCRIPTION
Output for the SW matrix.
Output for the SW matrix.
Output for the SW matrix.
Output for the SW matrix.
Ground
Input for the matrix return.
input for the matrix return.
Input for the matrix return.
Input for the matrix return.
Standby detector input.
Goes to standby at the end of a pulse.
Serial data output clock:
a) PLLN
b) CTCSS TONE
c) УО EXPANSION
Serial data output synchronized with CK.
BUSY input used when a signal is received.
Input used for lamp output HI/LOW control.
input used for ON/OFF control of SOL OFF and BEEP
output.
TX/Rx switching input.
Switches matrix input to FUNC functions.
Output for the initial matrix.