Invention of the telephone hardly a commercially practical telephone in the modern sense. Thomas Edison tested the Reis equipment and found that "single words, uttered as in reading, speaking and the like, were perceptible indistinctly, notwithstanding here also the inflections of the voice, the modulations of interrogation, wonder, command, etc., attained distinct expression." In 1947, the Reis device was tested by the British company Standard Telephones and Cables (STC). The results also confirmed it could transmit and receive speech with good quality (fidelity), but relatively low intensity. At the time STC was bidding for a contract with Alexander Graham Bell's American Telephone and Telegraph
Invention of the telephone receiver. Gray did not convert his caveat into a patent application until after the caveat had expired and hence left the field open to Bell. When Gray applied for a patent for the variable resistance telephone transmitter, the Patent Office determined "while Gray was undoubtedly the first to conceive of and disclose the (variable resistance) invention, as in his caveat of 14 February 1876, his failure to take any action amounting to completion until others had demonstrated the utility of the invention deprives him of the right to have it considered." The carbon microphone was independently developed around 1878 by