User manual

6.4 X.21 DB25(M) to DB15(F) adaptor Cable

For X.21 applications, we must use the DB-25 to DB-15 adaptor cable to connect to a X.21 DTE DB-15 male cable.

The pin out of cable on DB-25(male) Connector to DB-15(Female) (X.21) Connector

DB-25 Pin Signal DB-15 (X.21) Pin Description

1 FGND 1 Protective Ground

7 GND 8 Signal Ground

2 T 2 Transmit Data

14 T 9 Transmit Data

3 R 4 Receive Data

16 R 11 Receive Data

4 C 3 Request To Send

19 C 10 Request To Send

8 I 5 Data Carrier Detect

10 I 12 Data Carrier Detect

17 S 6 Receive Clock

9 S 13 Receive Clock

All signals are balanced. Meaning there is always a pair (+/-) for each signal, like those used in RS422. The X.21

signals are the same as RS422, so please refer to RS422 for the exact details.

The front view of DB-25(M) connector and DB-15(F) connector on this cable: