72 BELL SYSTEM TECHNICAL JOURNAL 



circuit employs heater type tubes and will operate from the a-c power 

 conversion unit mentioned above. Since it also obviates the need for 

 a 1000-cycle generator as a source of signaling current it is particularly 

 well adapted to the small office type of installation. 



Equipment Features 



As mentioned before the new terminal is much more compact than 

 those previously used. Formerly 2| bays of standard size were 

 required for the terminal proper and an additional bay for the auto- 

 matic regulating equipment. Now a complete terminal including the 

 regulating equipment can be mounted in one such bay with some space 

 left for miscellaneous equipment. 



The same degree of compactness has been applied to the new 

 repeater. A bay of standard size was formerly required for the 

 repeater proper with another bay for the automatic regulating equip- 

 ment when provided. Both are now provided in one bay and, as in 

 the terminal, some space is available for mounting other equipment. 



The assembly of the equipment panels of the carrier terminal and 

 repeater generally follows conventional practices, the repeating coils, 

 condensers, vacuum tubes, etc., being mounted on the front of steel 

 panels with the electrical terminals projecting through and the wiring 

 placed on the rear. The filters are in sealed cans with soldering 

 terminals brought out on the rear for wiring connections. 



In view of the wide field of use anticipated for the new system, 

 somewhat more than the usual flexibility of assembly and arrangement 

 of parts has been provided. In small terminal offices, that is, offices 

 having one or two systems, the four-wire terminating sets and asso- 

 ciated patching jacks and the carrier line equipment and associated 

 jacks may all be in one bay, using for this purpose the miscellaneous 

 bay space referred to above. Similarly, the line filter equipment may 

 be mounted on the repeater bay. 



In the larger terminal offices, in order to facilitate operation and 

 maintenance, the four-wire voice-frequency patching jacks can be 

 located in a central patching bay with similar jacks from other carrier 

 channels. Testing and monitoring equipment provided at such a 

 point will, therefore, be common to many circuits. In the same 

 manner the carrier frequency patching jacks of a large number of 

 terminals or repeaters in an office can be grouped at a central point. 



Line Considerations 



Since the new system occupies practically the same frequency range 

 as its predecessor, it can be applied to open-wire routes in very much 



