DELOCK 86617: Zero modem cable, RS-232, connector - socket with nuts, 3 m at reichelt elektronik
Null modem - Wikipedia
Amazon.com: SF Cable, 6 ft DB9 F/F Null Modem Cable RS232 : Electronics
RS-232 Null modem cable
FTDI FT231X USB to UART USB A TO DB9 Female RS232 Cross Wired Null Modem Cable for TV Box DVB STB|rs232 null modem cable|modem cablenull modem cable - AliExpress
What is null modem? Null Modem cable vs Straight serial cable
StarTech 10' DB9 RS232 Serial Female to Female Null Modem