he Sony 9-Pin Protocol or P1 protocol is a two-way communications protocol to control advanced video recorders. It uses an RS-422 D-sub 9-pin connector, where bi-direction communication takes place over a four wire cable.
Interface is based on RS-422 specifications.
|1||Frame ground||Frame ground|
|2||Receive A||Transmit A|
|3||Transmit B||Receive B|
|4||Transmit common||Receive common|
|5||Spare or ground||Spare or ground|
|6||Receive common||Transmit common|
|7||Receive B||Transmit B|
|8||Transmit A||Receive A|
|9||Frame ground||Frame ground|
Pins 2 and 7 form a pair and must be twisted together on long runs.
Pins 3 and 8 form a pair and must be twisted together on long runs.