9 pin D-SUB male connector.
The AT&T 6300 (sold in Europe as the Olivetti M24 and Persona 1600) uses a 9-pin DE-9 connector for its permanently attached keyboard cable, rather than the 5-pin DIN employed by IBM PC/XT and AT machines. The cable carries five active wires: +12 Vdc for keyboard power (in contrast to the IBM standard’s +5 Vdc), two grounds, and two bidirectional serial signal lines used to exchange scan codes with the host’s 8041A keyboard controller. The electrical protocol is otherwise compatible with the IBM PC/XT keyboard variant, making the 6300 broadly IBM-compatible whilst retaining its own proprietary physical interface.
| Pin | Name | Description |
|---|---|---|
| 1 | DATA | Data |
| 2 | CLOCK | Clock |
| 3 | GND | Ground |
| 4 | GND | Ground |
| 5 | +12V | +12 VDC |
| 6 | n/c | Not connected |
| 7 | n/c | Not connected |
| 8 | n/c | Not connected |
| 9 | n/c | Not connected |
Notes
The keyboard cable is permanently attached and shielded. Pins 6–9 are unused in the standard keyboard configuration. The +12 Vdc supply on pin 5 is a key electrical distinction from the IBM PC/XT/AT standard, which supplies +5 Vdc to the keyboard.
Signals
- DATA — bidirectional serial data line; carries scan codes (make and break) between keyboard and host.
- CLOCK — bidirectional clock line; generated by the keyboard during normal transmission; the host may inhibit it by pulling the line low.
- GND — signal and power return; two separate ground lines are provided (pins 3 and 4).
- +12V — keyboard power supply at +12 Vdc; distinct from the +5 Vdc used on IBM PC/XT/AT keyboards.