Science Art: Phone Tester for Electric Circuits, Patent No. 1,187,500; issued to G. B. Raymond.

Scientific illustration of early headphones used as a circuit tester in the 1900s.
Scientific illustration of early headphones used as a circuit tester in the 1900s.

These are not headphones, exactly. This is a thing made of telephone parts designed to help electrical tinkerers do better tinkering.

It’s from a page called “Latest Patents” in a tech magazine called The Electrical Experimenter from September 1915. (The facing page has a humorous “Phoney Patents” cartoon from the “Phoney Patent Offizz.” This issue, it’s an Aero Bed Fire Escape.)

This device is, according to the magazine, an…

Effective testing instrument for locating short and open circuits in electric wiring or dynamo and motor windings. It comprises an ordinary telephone receiver, headband, flashlight battery and test cords. The battery fits into a neat metal casing mounted on side of the head band as shown. The ‘phone, so used, constitutes one of the most sensitive testing devices known, superior in many ways to the galvanometer.

I guess it’s designed to crackle?