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 42
a group. All the combinations mentioned involve no new principles of struc-ture, mechanically or electrically. Exchanges Having More Than Nine or Ten Offices.—In an exchangewhich has more than nine or ten central offices, we can not take the firstselectors for office selectors alone. This is… … 3rd. Thou.
Telephone
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