Null Modem Cable Pinout (DB9-DB25). Pinout and signals for building a serial (RS232) nullmodem (crossed) cable

Use this cable between two DTE devices (for instance two computers).

DB9 pin D-SUB female to PC1 DB9 pin D-SUB female to PC1
DB25 pin D-SUB female to PC2 DB25 pin D-SUB female to PC2

DB9 DB25
Receive Data 2 2 Transmit Data
Transmit Data 3 3 Receive Data
Data Terminal Ready 4 6+8 Data Set Ready + Carrier Detect
System Ground 5 7 System Ground
Data Set Ready + Carrier Detect 6+1 20 Data Terminal Ready
Request to Send 7 5 Clear to Send
Clear to Send 8 4 Request to Send
Note: DSR & CD are jumpered to fool the programs to think that they are online.
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