Wall telephone with Blake transmitter, unknown maker, possibly the United Telephone Company, British, 1880-1900.
The Blake transmitter was the first successful telephone microphone. It was invented by Francis Blake (1850-1913) of Massachusetts in 1877. It used a platinum contact with a button of carbon to transmit speech, and was found to be more sensitive that earlier transmitter designs used in telephones. This telephone set was one of the earliest to be used in Britain, after a patent dispute over Blake's transmitter had been settled.