### X.21 Cabling

Use these diagrams as a reference when building or purchasing X.21 cables. See Tips for Building and Purchasing Cables for cable length and quality concerns.

DB-15 Pin Number | Signal | DB-15 Male Connector
2 | TxD (A)
9 | TxD (B)
3 | Control (A)
10 | Control (B)
4 | RxD (A)
11 | RxD (B) (B)
5 | Indicator (A)
12 | Indicator (B)
6 | Signal Element Timing In (A)
7 | Signal Element Timing Out (A)
13 | Signal Element Timing In (B)
14 | Signal Element Timing Out (B)
8 | Signal Ground
1 and shell | CGND