Sharp AR-M257 Key Operator's Manual page 126

Connectors
Caution:
This connector is only intended for service purposes.
Any connection to this terminal may cause malfunctions
of the copy machine.
Instruction for service technician:
The cable length for the service terminal has to be less
than 10 feet (3 m).
RSPF connector
Finisher connector
Parallel connector
USB connector