The X.21 interface is normally found on a 15-Pin D Sub connector.
The
pinout for the 15-pin connector is shown below.
X.21 used a state-driven
protocol running full duplex from 9600bps to 64 Kbps.
The X.21 interface
is out-dated, first being introduced in the mid 1970's.
The X.21
interface may also be found on other connector sizes.
Also refer to the
RS422 Electrical bus page which uses the same
signal.
The X.21 interface is obsolete, and may also be referred to as just X21.
| Pin Name | Pin Description |
|---|---|
| 1 | Shield |
| 2 | Transmit A |
| 3 | Control A |
| 4 | Receive A |
| 5 | Indication A |
| 6 | Signal Timing A |
| 7 | Terminal Transmit Clock A |
| 8 | Signal Ground |
| 9 | Transmit B |
| 10 | Control B |
| 11 | Receive B |
| 12 | Indication B |
| 13 | Signal Timing B |
| 14 | Terminal Transmit Clock B |
| 15 | Not Used |
Manufacturers of
D-Subminiature Connectors [D-sub Connectors].
Refer to the Buses icon below for descriptions of all other interface buses, including other cable buses.
Refer here for a listing OEM Manufacturers listed in alphabetic order.
Engineering Design Key words: X.21, ISO,CCITT, Balanced
differential Cable Bus, Electrical Standard, Interface Standard,
Specification, Electrical Interface, Semiconductor IC manufacturers,
Physical Interface, Engineering Description, Characteristics, Device,
X.21 pinout, pin out, Signal Assignments. What is the X.21 interface.
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