. The Bell System technical journal . 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 commerciala
. The Bell System technical journal . 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 Fig. 15—Power Machine and Control Equipment for Two 10,000-Line Units Storage batteries (Fig. 16) floating across the current supply bus-bars insure regulation. In addition to stabilizing the voltage andreducing noise interference from the machines and between tele-phone circuits, the batteries perform the important function of keep-ing the exchange in operation during interruptions to the commercialpower service. Small motor generators furnish current for ringingsubscribers bells and drive commutators supplying various tones andsignals. Batteries or machines supply current for operating coin 74 BELL SYSTEM TECHNICAL JOURNAL boxes and pulse machines provide impulses for the operation of cer-tain of the machine switching apparatus. Whenever practicable, two or more commercial power services fromindependent generating stations are secured, either of which will keepthe office supplied. Where independent generating systems are notavailable a reserve gas engine supply (Fig. 17) is instal
Size: 1790px × 1396px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
