Editing Serial port (section)

===DTE and DCE===
The individual signals on a serial port are unidirectional and when connecting two devices, the outputs of one device must be connected to the inputs of the other. Devices are divided into two categories: ''[[data terminal equipment]]'' (DTE) and ''[[data circuit-terminating equipment]]'' (DCE). A line that is an output on a DTE device is an input on a DCE device and vice versa, so a DCE device can be connected to a DTE device with a straight wired cable, in which each pin on one end goes to the same numbered pin on the other end.

Conventionally, computers and terminals are DTE, while peripherals such as [[modem]]s are DCE. If it is necessary to connect two DTE (or DCE) devices together, a cable with reversed TX and RX lines, known as a [[Crossover cable|cross-over]], roll-over or [[null modem]] cable must be used.