Panasonic KX-TR320EXF Service Manual page 25

connected, the built-in speakers (Main, Sub) is cut off and the
external speaker is driven.
20.2. TX Operation
RF Board:
During TX operation 3V is supplied from TXP of pin 11 of CN5 causing TX of pin 12 to Low (0V)
and Q14 to be turned ON to work the TX circuit. At that time RX of pin 10 becomes High (3V)
and Q12 is turned OFF, then the RX circuit stops working.
1. VR2 adjusts the level of the modulation signal (MOD) of CN5, then
the signal is input to the modulation terminal of VCO for TX (V2)
pin 3.
2. VCO (V2) oscillates by the TX frequency, amplified at IC7 and led
to pin 1 of PLL (IC5). The oscillation frequency of VCO is
controlled by PLL (IC5) divides the reference frequency of 21.25
MHz, and locks the frequency at 12.5 kHz step (phase comparison
frequency: 6.25kHz). The ratio of dividing frequency output from
CPU is programmed to the internal register from pin 7 as the
serial data.
3. The output from pin 4 of IC7 is input to Q11 (RF amplifier). The
power amplifier Q8 boosts the signal (approx.25 dBm) and the
signal is sent to pin 3 of IC4 (antenna switch).
4. The signal is output from pin 5 of IC4, passes through the low
pass filter, and it is transmitted from the antenna. At that time, the
antenna and pin 3 of IC4 is connected because pin 4 of IC4 is high
(Tx power on).
CPU Board:
When the TX operations, CPU programs the TX mode. IC 9 (C3V) is turned ON when
transmitting, and IC11 and IC13 are set to TX operation.
1. The voice input from microphone is sent to pin 3 of IC11 and
amplified. Then the amplitude is compressed at the compressor
circuit and scrambled. After limiting the amplitude, the signal is
output from pin 6 through the filter. At the same time the input
signal from the microphone is sent to pin 6 of IC14 to be