N-1 CARRIER TELEPHONE SYSTEM 



441 



subassembly; (2) the expander and signaling (voice frequency receiving) 

 subassembly; and (3) the carrier frequency subassembly. Provision is made 

 in the carrier frequency subassembly for automatic channel transmission 

 regulation. Subassemblies (1) and (2) are identical for all channels. An 

 exploded view of the expandor and signaling subassembly is shown in Fig. 18. 



Terminal Transmitting and Receiving Group Units 



The transmitting and receiving group units together contain the transmit- 

 ting and receiving amplifiers; the group modulator, which is used in either 

 the transmitting or receiving branch but not in both; the signaling oscil- 

 lator; and the carrier alarm circuit. Provision is made for automatic group 



Fig. 17 — Channel unit subassemblies. Compressor at left; expandor and signaling at 

 center; carrier at right. 



transmission regulation in the receiving circuit. There are four types of 

 group units: one high group transmitting, HGT, and one low group receiv- 

 ing, LGR, for a terminal which transmits the high group of frequencies and 

 receives the low group; and one low group transmitting, LGT, and one 

 high group receiving, HGR, for the reverse terminal. 



The group units are combinations of three of the following subassemblies 

 as required: (1) high group transmitting, (2) low group transmitting, (3) 

 high group receiving, (4) low group receiving and (5) oscillator. The oscil- 

 lator subassembly supplies the group carrier frequency and the 3700 cycle 

 signaling tone. The oscillator subassembly is plugged into a low group trans- 

 mitting or a low group receiving subassembly and the combination equipped 

 with a common can cover to form an LGT or an LGR unit. The addition 

 of a cover to the high group transmitting or high group receiving subas- 

 sembUes forms a complete HGT or HGR unit. 



