An adapter is a hardware device or software component that converts transmitted data from one presentation form to another. The data presentation can be, for example, a message sent between objects in an application or a packet sent through a network. A null modem adapter enables users to transform a normal serial cable into a null modem. It contains the necessary crosslinks between the signals. A null modem adapter converts any straight-through wired cable with connectors into a null modem "cross-wired" configuration. This configuration is suitable for many serial PC to PC and PC to printer applications.

25 pin female connector

25 pin male connector

25 pin D-Sub Male

Null Modem Adapter Pinout

Signal

Female

Male

Shield Ground

1

1

Shield Ground

Transmit Data

2

3

Receive Data

Receive Data

3

2

Transmit Data

Request to Send

4

5

Clear to Send

Clear to Send

5

4

Request to Send

Data Set Ready

6

20

Data Terminal Ready

Data Terminal Ready

20

6

Data Set Ready

Ground

7

7

Ground

The team at The Hardware Book contributed this data.