1. In a data station, the equipment that performs functions, such as signal conversion and coding, at the network end of the line between the data terminal equipment (DTE) and the line, and that may be a separate or an integral part of the DTE or of intermediate equipment.
2. The interfacing equipment that may be required to couple the data terminal equipment (DTE) into a transmission circuit or channel and from a transmission circuit or channel into the DTE. Synonyms data communications equipment (deprecated), data set (deprecated).
Source: from Federal Standard 1037C and from MIL-STD-188
DCE may also be an acronym for the Distributed Computing Environment, a specification from The Open Group.