The Free On-line Dictionary of Computing (30 December 2018):

Data Communication Equipment
Data Communications Equipment

    (DCE) The devices and connections
   of a communications network that connect the communication
   circuit between the data source and destination (the Data
   Terminal Equipment or DTE).  A modem is the most common
   kind of DCE.

   Before data can be transmited over a modem, the DTR (Data
   Terminal Ready) signal must be active.  DTR tells the DCE that
   the DTE is ready to transmit and receive data.

   DCE and DTE are usually connected by an EIA-232 serial
   line.  It is necessary to distinguish these two types of
   device because their connectors must be wired differently if a
   "straight-through" cable (pin 1 to pin 1, pin 2 to pin 2 etc.)
   is to be used.  DCE should have a female connector and should
   transmit on pin two and receive on pin three.  It is a curious
   fact that many modems are "DTE" according to the original
   standard.

   (1995-02-28)