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 229
ark in 1904 is used inScandinavia as an auxiliary to manual switchboards to distribute theload among A operators and among B operators. The systemfor promoting better distribution among A operators is called theOperators Aid System and is an application of the Christensen selec-tor devised by… … Fig. 185.-—View from below of three Chris- Fig. 186.—View from above of Christensentensen pneumatic selectors. pneumatic selectors.
Telephone
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