. The Bell System technical journal . te it is obviates the necessity for restrictions in the design of eitherthe dialing circuit or the selecting circuit, such as would be necessaryif they were tied together. Power Supply Arrangements. Since most of the operations normallyrequired in handling a call in a machine switching office are carriedout mechanically, it is evident that a considerably larger amount ofpower is required than with the manual system. Selectors andsequence switches are propelled mechanically by rotating shaftsdriven continuously by small motors mounted on each
. The Bell System technical journal . te it is obviates the necessity for restrictions in the design of eitherthe dialing circuit or the selecting circuit, such as would be necessaryif they were tied together. Power Supply Arrangements. Since most of the operations normallyrequired in handling a call in a machine switching office are carriedout mechanically, it is evident that a considerably larger amount ofpower is required than with the manual system. Selectors andsequence switches are propelled mechanically by rotating shaftsdriven continuously by small motors mounted on each frame. The use of small motors on each frame gives a flexible and reliablesource of power particularly since the motors now being used are ofthe special duplex type developed for the purpose. They consist 72 BELL SYSTEM TECHNICAL JOURNAL of two motor elements in one frame, one element being normallydriven from the commercial power service and the other being drivenby the telephone reserve storage battery to which it is automatically. Fig. 14—Group of Typical Selector Frames connected by a relay inside the motor when the regular power power failure, therefore, causes no interruption to the drive. Theselectors are arranged so that not more than half in any one group are MACHINE SWITCHING TELEPHONE SYSTEM 73 driven by the same motor which insures continuous service in caseof motor failure. The main power requirement is for direct current at about 24 and48 volts which is furnished from motor generator sets (Fig. 15) ofspecial construction to reduce noise, converting the commercialalternating or direct power current into current which is regulatedas to voltage and is free from variations which would cause noise inthe telephone circuits.
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