Null modem cable (DB9-DB9). Pinout and signals for building a serial (RS232) nullmodem cable

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

DB9 pin D-SUB female to PC1
DB9 pin D-SUB female to PC1
9 PIN D-SUB FEMALE
DB9 pin D-SUB female to PC2

DB9-1 DB-2
Receive Data 2 3 Transmit Data
Transmit Data 3 2 Receive Data
Data Terminal Ready 4 6+1 Data Set Ready + Carrier Detect
System Ground 5 5 System Ground
Data Set Ready + Carrier Detect 6+1 4 Data Terminal Ready
Request to Send 7 8 Clear to Send
Clear to Send 8 7 Request to Send

Note: DSR & CD are jumpered to fool the programs to think that they are online.

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