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 389
. 291) is used to compare the speed of a calling device connected to itwith a standard. The essential parts of the indicator are two indicat-ing fingers, each of which is fastened to a small wheel, arranged so thatit may be rotated from left to right through an arc of approximately90 deg. The power… … Fig 291.—Calling deviceindicator. speed POWER PLANT, SUPERVISORY AND TESTING EQUIPMENT 365 second. The escapement of the other ratchet wheel is controlled by anelectromagnet, linked with the line of the calling device to be tested.The ratchet wheel and finger escapes one step for each…
Telephone
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