TECHNES Encyclopedia Database

Here we will focus on the oscilloscope. In France, a new application began to be tried out. This was the galvanometer oscillograph, invented by the roads and bridges engineer André Blondel in 1893.^[4] This instrument was based on the same principles as the Deprez-d’Arsonval moving coil galvanometer (1882), an instrument used to observe the existence, direction and intensity of currents and whose construction was based on the guiding action of currents on magnets. Blondel, who worked at the time on the properties of synchronous and non-synchronous motors, sought to record the curves of alternating currents. He brought to the “classical” galvanometer new elements such as a small moving mirror, an optical condenser, a lamp and a darkroom in which the photographic paper could move. The recording he succeeded in obtaining followed this schema:

the beam of light coming out of an optical condenser and limited by a diaphragm was reflected onto the mirror of the oscilloscope and was then focused by a cylindrical lens in the form of a spotlight leaving the trace of its vibrations on the sensitive film.^[5]

Following numerous tests, Blondel finally presented this improved version of his oscilloscope (sometimes known as a “bifilar oscillograph”) to the Académie des sciences on 11 November 1901. Afterwards, the oscilloscope was manufactured by Ateliers Jules Carpentier. It was improved on numerous occasions and supplanted much later by the cathode-ray oscilloscope.

Although Blondel’s oscilloscope was mass-produced to meet the needs of the electrical industry, it remained the case that his recording system was the prototype for wave systems taken up by other scientists working on tangibly different topics, such as the physiology of speech or human locomotion, but also by the pioneers of synchronized sounds and moving images. In Claude Lerouge’s description:

it was thus natural that people thought to use this device to record voices or music on cinema film stock. It was so well designed that it was necessary only to make a few minor modifications to it in order to adapt it to sound recording.^[6]

Despite the abundance of these experiments, none of these techniques could reproduce the sound that had been recorded on a piece of celluloid film or sensitized strip of paper. Before 1900, therefore, no one had yet succeeded in reproducing the sounds recorded by the systems described above. The first tests on the path to recreating sound were those of Ernst Ruhmer, a German physicist, and two Frenchmen, Eugène Lauste and Henri Joly. Ruhmer began working on this idea in the late nineteenth century, inventing around 1902 a device for reproducing the sounds recorded on film stock, to which he gave the name photographophone.