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 167
ndividual lines. To obviate this rapid use of numbers, fourth selectors are installedfor the party lines alone. This gives the party line numbers one moredigit than the individual lines, 6 digits in a 5-digit exchange. Midway Office Without Through Trunking.—Sometimes betweentwo separate exchanges… … Fig. 146.—Midway office without through trunking. changes are connected by toll service. It can be arranged so thatalthough each exchange can call the midway office, it can not call throughto the other office. Assume the midway office be No. 2 (Fig. 146) and that the twoexchanges are represented by…
Telephone
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