The twang of a reed
This idea was clear in Bell’s mind by the summer of 1871, but he did not then know how to reduce it to practice. On June 2, 1875, he succeeded in doing so. In adjoining attic rooms at 109 Court Street, Boston, he and Watson were trying out several pairs of harmonic telegraph instruments each consisting of an electromagnet with a steel organ reed vibrating over it. One reed stuck. Watson plucked it with his finger to start it again, but it did not come free, so Bell heard an unusual sound. Instead of hearing a series of electric pulsations, he recognized the twang of a vibrating reed! He knew then that, as Watson has put it, “he was hearing, for the first time in human history, the tones and overtones of a sound transmitted by electricity.” That afternoon Bell directed Watson to make the instrument that was to be the first Bell telephone. This instrument transmitted voice tones, but not until March 10, 1876, did Bell succeed in transmitting an intelligible sentence of speech.