Technical manual TM (series). 11-2222. Receiving transmitter distributors, TT-12/FGQ-1, TT-13/FGC-1, and transmitter distributors, TT-21/FG, TT-25/FG, TT-26/FG, TT-52/FG (including other teletype model 14 transmitter distributors) [with list of references]; May 1951.