Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems (1921)
Smith, Arthur Bessey, b. 1875, Campbell, Wilson Lee · New York : McGraw-Hill · leaf 383
ng. The main central office battery on the power board is protected byenclosed fuses. These fuses have alarm relays across their terminals, 358 .4 U TOM A TIC TELEPHON Y two windings taking care of four fuses. Each relay locks mechanicallyand lights the red tell-tale lamp marked Power Board. The… … relay common to the first selector boards. This relay lights the tell-talelamp on the ceiling. The lineswitch boards are similarly protected, except that the fusealarm strip is connected directly to the fuse pilot lamp. The circuit breakers are provided with one .1300-ohm relay to indi-cate…
Telephone
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