DB9 (RS-422, device side) pinout
DB9 RS-422 Pinout (Sony 9-Pin)
The Sony 9-pin (P2) machine-control interface runs RS-422 over a DB9: two differential pairs (transmit and receive) plus grounds, controller to device. The table below gives the device (deck/server) side; the controller mirrors transmit and receive.
| Pin | Signal | Notes |
|---|---|---|
| 1 | Frame ground | Chassis/shield. |
| 2 | Receive A (−) | Data into the device, inverted leg. |
| 3 | Transmit B (+) | Data out of the device, non-inverted leg. |
| 4 | Transmit common | Signal ground for the transmit pair. |
| 5 | Spare | Unused in standard P2 control. |
| 6 | Receive common | Signal ground for the receive pair. |
| 7 | Receive B (+) | Data into the device, non-inverted leg. |
| 8 | Transmit A (−) | Data out of the device, inverted leg. |
| 9 | Frame ground | Chassis/shield. |
What it’s used for
RS-422 9-pin is the survivor of the tape era: video servers, replay systems, and broadcast automation still speak the Sony P2 protocol for transport control (play, cue, jog, timecode requests) because everything understands it and it just runs.
The differential pairs give it the long-cable noise immunity RS-232 lacks; runs of 100 m and more are routine in plant wiring.
Wiring & termination notes
- Controller-to-device cables cross the pairs: controller transmit lands on device receive. A "straight" cable that works between one pair of devices may be wrong for the next; check which side each box wires as.
- Direction confusion is the whole failure mode of 9-pin: if control is dead, swap TX/RX pairs before anything else. Purpose-built "9-pin turnaround" adapters exist for exactly this.
- Use shielded twisted-pair cable with the pairs kept intact (one pair TX, one pair RX); flat serial cable defeats the differential noise rejection.
- Some devices deviate from the standard table or make pins switchable in menus; the device manual is authoritative when a port misbehaves.
Frequently asked questions
Is RS-422 the same as RS-232?
No. RS-422 is differential (two wires per direction), supporting long runs and higher noise immunity; RS-232 is single-ended. The DB9 shell is shared, the electricals are not, and they do not interoperate directly.
What is Sony 9-pin control used for today?
Transport control of video servers and replay systems: play, stop, cue to timecode, jog. Broadcast automation and show playback controllers still ship with 9-pin because the installed base is enormous.