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

EIA-232C

    The EIA equivalent of ITU-T
   standard V.24.

   The EIA EIA-232C electrical signal is unbalanced +/- 5 to +/-
   12V, polar non return to zero and handles data speeds up
   to 19.2 kilobits per second.

   [Correct name?  Relationship to RS-232C? Difference from
   EIA-232?]

   (2004-08-02)