Patent Model - Improvement in Duplex Telegraph Instruments

Maker and role
Joseph Stearns (b.1831, d.1895), Patentee
Production date
Feb 25 1873
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Object detail

Walnut (visual), brass, steel
9 3/8 x 9 7/8 x 2 1/8" (23.8 x 25.1 x 5.4cm)
Stearns's invention "relates to apparatus for the simultaneous transmission of two signals from opposite ends of the same line-wire; and consists of a key of the peculiar construction..., and of its combination with a magnet or coil excited by the main-line battery, a neutralizing or opposing magnet or coil excited by an equating battery, and a suitable resistance for the purpose of preventing the receiving magnet or relay, though always in the circuit, from being affected by currents transmitted from the home station." (Patent Number 136,274)
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