GoTo ConnectorCONNECTORGoTo Main


Common names: ITU-TSS (CCITT) X.21, ISO 4903

15 PIN D-SUB MALE (at the DTE)
15 PIN D-SUB FEMALE (at the DCE)


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

X.21 Page at Connectivity Knowledge Platform (Made IT)

Copyright © The Hardware Book Team 1996-2001.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2001-06-07