Date: January 7, 1896
Creator: Oram, John M.
Description: Patent for an apparatus for protecting electrical circuits, and is an improvement on a previous patent (No. 537,932) issued to the inventor. This patent consists of "an electrical circuit, an alarm or indicator, a continuously-operating signal-transmitter at the protected structure operating to affect or influence the alarm or indicator, and a second or duplicate continuously-operating signal-transmitter located at the watchman's station, operating in unison with the first-named signal-transmitter to affect the alarm or indicator equally and oppositely as regards the first-named transmitter, whereby a signal is sounded or an alarm given only when the two transmitters are out of unison or when one is changed, varied, or interfered with in an unauthorized manner" (lines 72-86).
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