Review on 🔌 Industrial Electrical RS232 Serial Cable Communication by DTECH by Justin Ott

The description says: Connected as a null modem cable to a 9-pin serial port, 2-3 lines of which are crossed (only TX/RX and data lines are connected) to ground signal wires ); the standard is shielded with aluminum foil And it is true that pins 2 and 3 are optionally bridged, but it is not true that only TX and RX are grounded. All other pins are connected directly, which means that if you connect it to another DCE device, both sides will try to drive the same lines. Even if you don't have a handshake, you can still get into trouble if the two sides fight each other. The manufacturer's solution would be to either cross (pins 4 and 6) and (pins 7 and 8) or, as the description says, assume there is no handshake and leave all other pins unconnected. That means having only 3 wires in the cable.