The Gallows Model

Because of its fanciful resemblance to a hangman’s scaffold when turned on end, historians have labeled this instrument the Gallows Model. It was Alexander Bell’s first attempt to produce a speaking telephone, and was built by his assistant, Thomas Watson, based on a crude drawing Bell had given him sometime in June of 1875.

Earlier, Bell had been experimenting with his multiple-message harmonic telegraph concept when he noticed that one of the tuned reed relays in his system (essentially an electromagnet with a spring-like armature or reed) started to vibrate for no apparent reason. Learning that Watson had caused the effect when he plucked the reed of stuck reed relay, Bell told Watson to try plucking the other reed relays in the system, each set to vibrate at a different frequency. To his great surprise, Bell discovered that, by holding the first reed relay against his ear, he could hear the different frequencies of all the other relays in the system. It was a result he hadn’t expected, and he excitedly sketched out an idea that had just now occurred to him.

Watson’s rendition of that sketch, the Gallows Model, was simply a refined version of the reed relay described above. It was essentially a reed relay with its armature glued to a parchment membrane or diaphragm. With this, Bell hoped to prove what the original reed relay had merely promised - that he could now transmit articulate speech over a telegraph wire.

Bell connected the Gallows Model to several cells of a battery and to the previous reed relay. While Watson listened on the reed receiver, Bell shouted into the diaphragm of the instrument. Watson claimed that he could hear “vocal sounds” coming from the reed receiver, but he couldn’t make out what Bell was saying. They switched places and Watson shouted while Bell listened. Again, no speech was heard. Disappointed, Bell called the experiment a failure.

About a month later, a second Gallows Model was built. With these two instruments and several battery cells connected together, the original experiment was repeated, but with the same disappointing results. Technically, those Gallows Models should have worked, and, ironically, models made years later actually did work. The problem with the two original versions was not one of design, but of implementation. Based on later research and analysis, it appears that the resistance of Bell’s relays was too low for the relatively high battery voltage being used, resulting in very low efficiency. Later reproductions corrected this problem. But despite his disappointment, Bell knew that in July of 1875 he had sent some kind of "vocal sounds" over a wire. Those two words would later appear in his famous patent.

This page was written by A. Edward Evenson, Author of the book The Telephone Patent Conspiracy of 1876 available at

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