Panasonic KX-TR320EXF Service Manual page 29

21.3. Control Circuit
Condition
Voltage (4.5V) Supplied from External Power Source
21.3.1. Power Supply Will Not Be ON.
21.4. Reception Trouble/ RF Circuit
Condition
Channel No. Setup
SSG Frequency Setup
Standard Modulation (1KHz)
C3V Normally Applied
CN5 (Pin10: RX) LOW
21.4.1. Cannot Receive