CSD
Constant-speed drive. A component used with either aircraft gas turbine or reciprocating engines to drive AC generators. The speed of the output shaft of the CSD is held constant while the speed of its input shaft varies. The CSD holds the speed of the generator, and the frequency of the AC constant as the engine speed varies through its normal operating range.
Aviation Maintenance Technician Handbook — Powerplant, p. G-8
Taught in AF-K Quick reference, PP-F Quick reference.