Replica of Bell's tuned reed telephone receiver, made by Bell Telephone Laboratories Inc, Albany, New York, United States, 1925-1958.

This was the immediate precursor to Alexander Graham Bell's (1847-1922) 'Gallows' telephone. While Bell and his assistant Thomas Watson were testing the harmonic telegraph, Bell heard a sound coming through the receiver. This was not the frequency the reed had been tuned to, but the actual sound of Watson plucking the string. A contact screw had been wound too tightly, allowing for the continuous current that is essential for transmitting speech. Bell's next development was his 'Gallows frame' telephone, which could transmit indistinct speech.