I then changed
the pitch of the vibration, and found that the pitch of the sound under
my hand was also changed, agreeing with that of the vibration.' Gray
lost no time in applying this chance discovery by designing the
physiological receiver, which consists of a sounding-box having a zinc
face and mounted on an axle, so that it can be revolved by a handle.
One wire of the circuit is connected to the revolving zinc, and the
other wire is connected to the finger which rubs on the zinc. The
sounds are quite distinct, and would seem to be produced by a
microphonic action between the skin and the metal.
All these apparatus follow in the track of Reis and Bourseul--that is to
say, the interruption of the current by a vibrating contact. It was
fortunate for Bell that in working with his musical telephone an
accident drove him into a new path, which ultimately brought him to the
invention of a speaking telephone. He began his researches in 1874 with
a musical telephone, in which he employed the interrupted current to
vibrate the receiver, which consisted of an electro-magnet causing an
iron reed or tongue to vibrate; but, while trying it one day with his
assistant, Mr. Thomas A. Watson, it was found that a reed failed to
respond to the intermittent current.
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