Silvanus P Thompson's 'valve' telephone, 1882-85.
© Science Museum / Science & Society Picture Library
The New Telephone Company, formed in 1885, offered these telephones for sale at £16 a pair, in competition with the United Telephone Company which, with acces to Edison and Bell patents, offered a year's rental for £16. The human voice was used to open or close a valve which regulated the electric current. The microphone, a carbon ball resting on three carbon points at the end of a speaking tube, resembled a mechanical ball valve. The receiver used a parchment diaphragm, which Bell had rejected. It was found to infringe the Edison and Bell patents and the New Telephone Company was forced into liquidation in 1889.