Advertisement for the telephone, 1877.
© Science Museum / Science & Society Picture Library
A circular produced by Alexander Graham Bell's (1847-1922) agent Reynolds. This shows that in his original system the same design of instrument was used as both transmitter and receiver. After experimenting with various acoustical devices, Bell produced the first intelligible telephonic transmision with a mesage to his asistant on 5 June 1875. He patented this device as the telephone in 1876.