V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

DS3
       Digital Signal level 3 (T3), "DS-3"


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

DS3

    The third DS level, a framing
   specification for digital signals in the North American
   digital transmission hierarchy.  A DS3 signal has a
   transmission rate of 44.736 Megabits per second.

   DS3 is used, for example, on T3 synchronous Integrated
   Services Digital Network lines.

   (1995-01-12)