Description
Autograph Letter Signed, to Mr. Trotter, making arrangements for their meeting. A good one page example, 7 x 4½ inches, Board of Trade, 10 July 1889. Major Philip Cardew, Royal Engineers (1851-1910), inventor of the voltmeter, the vibratory transmitter for telegraphy, and other electrical devices. Cardew’s invention of the vibratory transmitter for telegraphy was perhaps his most important, and in the case of faulty lines it proved useful not only on active service overseas but also during heavy snowstorms at home. He received a money reward for this from the imperial and Indian governments. The utility of the invention was greatly extended by his further invention of ‘separators’, consisting of a combination of choking coil and two condensers. These instruments enabled a vibrating telegraph circuit to be superimposed on an ordinary Morse circuit without interference between the two, thus doubling the message-carrying capability of the line. His apparatus for testing lightning conductors was adopted by the war department. [DNB]