Time-division multiplexer for use with TSEC/KO-5 crypto gear - it interfaces with 16 channel frequency-division multiplexer for RTTY.

FUNCTIONAL DESCRIPTION The AN/UGA-1 is designed to accept multiplexed output of sixteen (16) channel multiplex equipment and divides it into sixteen (16) separate channels which are synchronously related to each other. Output on each channel is in six (6) unit synchronous signal. The receive portion of the equipment performs companion function.
RELATION TO OTHER EQUIPMENT The AN/UGA-1 is designed to be used with but not part of AN/UGC-3() for use on frequency division telegraph systems.
TYPE OF DIVISION: Time-division type. 
TYPE OF OPERATION: Neutral. 
TYPE OF ACTUATION: DC actuated. 
NUMBER OF CHANNELS: 16. 
NUMBER OF WORDS PER MINUTE: 60, 75, 100 words per minute per channel. 
RELATION OF CHANNELS INPUT AND OUTPUT: The 16 channel inputs and outputs are synchronous in nature and are synchronously related.

The KO-5 crypto system is a monster-

https://www.navy-radio.com/crypto/KO5CSP6620A.pdf