The Reis Receiver 1862-1872


The Reis Receiver (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 receiver for his telephone transmitter. He was then an instructor in physics (or natural philosophy, as it was then called) in Friedrichsdorf, Germany. The Reis Receiver was unique in telephone history, and he was the only one known to have used this unusual design.

At first glance, one might assume that it was simply another type of electro-magnetic receiver, similar to those used by practically all of the other early telephone experimenters. However, it did not work by magnetic attraction and repulsion. Instead, it worked by a little-known phenomenon called magnetostriction.

Magnetostriction causes certain ferrous metals and alloys, an iron rod for instance, to become longer or shorter when under the influence of a fluctuating magnetic field. This effect was observed by several early experimenters (J. Joule and C. G. Page) in about 1840. Page noted that an electromagnet would emit a strange click when pulsed with a sudden current, and deduced that the sound was caused by the iron core of the electromagnet actually changing its length under the influence of the surrounding magnetic field. He called the effect “galvanic music,” but found no practical use for it.

This was the technique Reis chose to make the receiver for his telephone transmitter. In his first implementation, he merely wrapped a coil of wire (or helix as he called it) around an iron knitting needle and stuck the needle into one of the S-holes in a violin, which served as a sounding board. He later refined the design, as shown in the illustration, by clamping the iron rod, surrounded by a coil of wire, to a cigar-box type of resonator. The fluctuating sound currents in the helix caused the rod to change its length in step with the fluctuations, which, in turn, caused the box to resonate. Note that there are no moving parts, per se, in a Reis receiver. In fact, for the receiver to function properly, it is essential that all the parts be tightly clamped
together.

Because the Reis receiver requires a fairly high level of current, it is not as sensitive as the common electro-magnetic receivers, although Reis was able to transmit largely understandable speech. However, when driven with a modern amplifier, it can generate enough volume to be heard throughout a small room, and with a fidelity rivals that of an inexpensive loudspeaker.


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