Every pin in the interface has its function detailed in the following table. The first column gives the pin number on the 36-way Centronics connector (printer end) while the second column shows the matching pin number on the 25 way D plug at the PC end. The asterisks shows those functions which vary between different printers. The third column shows the signal name, and the fourth column gives the direction from the printer's point of view.
| Printer Pin | Computer Pin | Signal Name | Directn (Ptr) | Function |
| 1 | 1 | STROBE- | IN | Data Ready (0.5uS Pulse) |
| 2 | 2 | DATA1 | IN | Data Line |
| 3 | 3 | DATA2 | IN | Data Line |
| 4 | 4 | DATA3 | IN | Data Line |
| 5 | 5 | DATA4 | IN | Data Line |
| 6 | 6 | DATA5 | IN | Data Line |
| 7 | 7 | DATA6 | IN | Data Line |
| 8 | 8 | DATA7 | IN | Data Line |
| 9 | 9 | DATA8 | IN | Data Line |
| 10 | 10 | ACK- | OUT | Data Received (9uS Pulse) |
| 11 | 11 | BUSY | OUT | Unable to Receive |
| 12 | 12 | PAPER OUT | OUT | Paper Empty |
| 13 | 13 | SELECT | OUT | Printer On-Line |
| 14* | 14 | AUTO FEED- | IN | Extra Line Feed at End |
| 15 | Unused | |||
| 16 | GND | Ground | ||
| 17* | CHASSIS GND | Earth | ||
| 18* | +5V DC | OUT | External 5V Supply | |
| 19-30 | 18-25 | GND | Ground | |
| 31 | 16 | RESET- | IN | Resets Printer |
| 32 | 15 | ERROR- | OUT | Printer Error |
| 33 | GND | Ground | ||
| 34 | Unused | |||
| 35* | Unknown | OUT | ||
| 36* | 17 | SELECT IN- | IN | Turns Printer On-Line |
Signals marked '*' are not consistant on all equipment
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