RS-232 EQUIPMENT TYPES

 A piece of equipment connected to an RS-232 line can either be
 a DCE (Data Communications Equipment, also known as a modem) or
 a DTE (Data Terminal Equipment, also known as a terminal or
 computer).  The major difference between the two are the wires
 on which each transmits or receives data.

 Few wiring problems will be found connecting DCE to DTE (computer to
 modem).  Connecting DTE to DTE or DCE to DCE can be fraught with
 peril, since so many different ways of implementing RS-232 are
 extant.  When DTE (computer) is connected to DTE (computer), the
 cable that goes between them must be wired speciall, and is called
 a "null modem".