Asynchronous Signals
DB9 to DB25 converter wiring (9 wires)
DB9 to DB9 dumb null wiring (3 wires)
DB9 to DB9 null wiring (7 wires)
DB9 to DB9 null wiring loop back handshaking (3 wires)
DB9 to DB9 null wiring partial loop back handshaking (7 wires)