Bell Telephone Company companies and to provide further funds for expansion of its overall telephone infrastructure. On April 17, 1880, National Bell was split into the American Bell Telephone Company, led by Theodore Vail as general manager, and with the International Bell Telephone Company (IBTC) as a holding company for its international subsidiaries. IBTC's first non-North American subsidiary was the Bell Telephone Manufacturing Company (BTM), established by Hubbard at Antwerp, Belgium, in 1882. The Bell System's Bell Telephone Company of Canada subsidiary, wholly owned by the National Bell, had been established two years earlier. Alexander Graham Bell's ten shares of Bell Telephone Company
Alexander Graham Bell 1876, Bell focused on improving the electromagnetic telephone and never used Gray's liquid transmitter in public demonstrations or commercial use. The question of priority for the variable resistance feature of the telephone was raised by the examiner before he approved Bell's patent application. He told Bell that his claim for the variable resistance feature was also described in Gray's caveat. Bell pointed to a variable resistance device in Bell's previous application in which Bell described a cup of mercury, not water. Bell had filed the mercury application at the patent office a year earlier on February 25, 1875, long before