Panasonic FP2 - Manual (Page 32)

FP2−CCU RS232C Port Wiring
4 − 4
4.1 RS232C Port Signals
CD (Receive Carrier Detect)
This signal goes on when the reception signal is within the specified range.
With the FP2 Computer Communication Unit, input to this terminal is invalid, so no
connections are necessary.
ER (Equipment Ready)
This signal notifies the partner device that the Computer Communication Unit is ready
for operation. The ER signal of the Computer Communication Unit is constantly on.