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Title:
Messenger-call circuits and switching apparatus therefor
United States Patent 1640325


Inventors:
Janson, George W.
Application Number:
US5891125A
Publication Date:
08/23/1927
Filing Date:
09/26/1925
Export Citation:
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Assignee:
WESTERN UNION TELEGRAPH CO
Primary Class:
340/292
International Classes:
H04M3/08
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