The Reis Transmitter 1862-1872

The Reis Transmitter (developed before A.G. Bell invented the telephone)

The instrument shown was developed by Philipp Reis in the early 1860s and was used as the transmitter, the companion piece for his telephone receiver. He was then an instructor in physics (or natural philosophy, as it was then called) in Friedrichsdorf, Germany.

This enigmatic instrument was condemned by the courts as a non-telephone, incapable of transmitting speech, because it was based on a “false theory.” Yet, at the same time, it was acknowledged by many engineers and scientists as the first device to carry the human voice. So what is the story behind this unusual telephone.

The instrument went through several design phases, the model shown being the last version. However, the principle of operation was essentially the same in all cases. In this version, a platinum contact was glued to the center of a parchment diaphragm. Directly above this contact, resting by gravity, was a second platinum contact. In operation, these contacts where connected to a battery and Reis’ receiver, forming a simple series circuit. Words spoken into the mouthpiece caused the diaphragm to flex up and down in step with the vocal sounds and vary the pressure (and thus the resistance) on the closed contacts, consequently modulating the current to the receiver. Or did those same sounds cause the contacts to actually separate, i.e., open and close? This was the crux of the argument, and this is where the court’s deadly “false theory” comes in.

During the late 1870s it was widely held that articulate speech could not be transmitted by abrupt, make and break currents; that such speech could be reproduced only by smooth, continuously varying currents. In Reis’ written account of how his telephone worked, he described it as a “make and break” system, with the contacts opening and closing. He explained it that way because it was the only mode that made sense to him, based on the electrical knowledge of his day. Unfortunately, he was wrong. Although his transmitter could and often did operate in that manner, it could also operate in the so-called loose contact variable pressure mode (now known as the microphone mode) and transmit true, articulate speech. The only problem was that Reis never learned of this, having died in 1874, shortly before the microphone principle was discovered. But Reis’ make and break description was fatal to his claim that he could transmit the human voice. In the peculiar logic of the courts, it couldn’t transmit articulate speech, despite testimony to the contrary, because it was based on a false theory (i.e., Reis’ own description).

There is no question that a Reis transmitter was a tricky and temperamental instrument, and that some were much better than others. The main problems were the parchment diaphragm (see Centennial Transmitter) and the metallic or platinum contacts. Metallic contacts, although capable of operating in microphone mode, cannot compete with carbon in that application. When made with carbon contacts, the Reis transmitter is essentially the same in function and principle as any of the other carbon transmitters that dominated the telephone industry for over a century.

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

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