The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 37
,the centre portion of which is replaced by a round rod of ebonite. Thepowerful action of the instrument may be due to a resonant action betweenthe two diaphragms. It is wound with a very large number of turns ofwire having a resistance of 350 . The efficiency of this instrument maybe gathered from… … Figure 13. working Wheatstone, and this with an earthed return wirel Thisexperiment was tried almost as a joke, but since then the instrument hasbeen much used in Manchester for this purpose. It is, however, truethat no double pole receivers have been wound to this resistance with theother parts on…
Telephone · Postal service
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