Editing Data terminal equipment (section)

==Connections==
Two different types of devices are assumed on each end of the interconnecting cable for a case of simply adding DTE to the topology (e.g. to a [[Ethernet hub|hub]], DCE), which also brings a less trivial case of interconnection of devices of the same type: DTE-DTE or DCE-DCE. Such cases need [[crossover cable]]s, such as for the [[Ethernet]] or [[null modem]] for [[RS-232]].<ref>EIA standard RS-232-C: Interface between Data Terminal Equipment and Data Communication Equipment Employing Serial Binary Data Interchange. Washington: Electronic Industries Association. Engineering Dept. 1969. {{OCLC|8250964307}}.</ref>

[[D-sub]] connectors follow another rule for [[RS-232#Connectors|pin assignment]].
* 25 pin DTE devices transmit on pin 2 and receive on pin 3. 
* 25 pin DCE devices transmit on pin 3 and receive on pin 2.
* 9 pin DTE devices transmit on pin 3 and receive on pin 2. 
* 9 pin DCE devices transmit on pin 2 and receive on pin 3.