A simple Null Modem cable has no hardware handshaking. This cable has only the data and signal ground wires connected. All of the other pins have no connection. With this type of cable flow control has to be implemented in the software. The use of this cable is restricted to data-traffic only on its cross-connected Rx and Tx lines. This cable can also be used in devices that do not need or make use of modem control signals.
| DB9 (Female) Pin | DB9 (Female) Name | DB9 (Female) Name | DB9 (Female) Pin |
|---|---|---|---|
| 2 | RXD | 3 | TXD |
| 3 | TXD | 2 | RXD |
| 5 | GND | 5 | GND |
