Common names: ITU-TSS (CCITT) X.21, ISO 4903
(at the DTE)
(at the DCE)
CORRECT?
15 PIN D-SUB MALE at the DTE (Computer).
15 PIN D-SUB FEMALE at the DCE (Modem).
| Pin | Name | Dir | Description | Type |
|---|---|---|---|---|
| 1 | n/a |  |
Shield | Ground |
| 2 | T (A) |  |
Transmit (A) | Data |
| 3 | C (A) | |
Control (A) | Control |
| 4 | R (A) |  |
Receive (A) | Data |
| 5 | I (A) | |
Indication (A) | Control |
| 6 | S (A) | |
Signal Timing (A) | Timing |
| 7 | B (A) | |
Byte Timing (A) | Timing |
| 8 | G | |
Ground | Ground |
| 9 | T (B) | |
Transmit (B) | Data |
| 10 | C (B) | |
Control (B) | Control |
| 11 | R (B) | |
Receive (B) | Data |
| 12 | I (B) | |
Indication (B) | Control |
| 13 | S (B) | |
Signal Timing (B) | Timing |
| 14 | B (B) | |
Byte Timing (B) | Timing |
| 15 | unused |
Note: Direction is DTE (Computer) relative DCE (Modem).
| Contributor: | Joakim Ögren |
| Source: | X.21 Page at Connectivity Knowledge Platform (Made IT) |
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Document last modified: 2002-01-13