Acousticon Model RF "Multi-Acousticon" Carbon Hearing Aid

The Acousticon model RF, the Multi-Acousticon, was one of, if not, the largest carbon hearing aids made.

It was manufactured by Dictograph Products, Inc. of New York and was marketed between 1910 and 1923. At that time it cost $85.00.

It measures 8" in height, 6¾" in width and 3½" in depth. It weighs a hefty 3 pounds when fitted with its battery.

Because the loudness of the early carbon hearing aids was dependent on the current flow through the earphone, amplification was controlled by the battery voltage, the resistance of the carbon microphone(s) and the padding resistors in the step-type volume control featured on many of the aids. When more amplification was needed, several carbon microphones could be wired in parallel to increase the current flow even more.

The Acousticon RF could be used with a 3, 4½ or 6 volt battery.

Some manufacturers produced carbon hearing aids with  two, three or four carbon microphones wired in parallel. The Multi-Acousticon had four carbon microphones wired in parallel. They were arranged in a square pattern (see picture at right).

There was also a small toggle lever just above the name Multi-Acousticon on the front of the microphones. (You can see this better in the larger picture.) This lever appears to somehow dampen the microphones to reduce the high frequency response.

Note: not all the Multi-Acousticon aids had this switch.

The large carrying case not only contained the carbon microphones, but also housed the battery, the earphone, a headband, a telescoping handle and a small screwdriver to tighten the connection terminals.

The volume control was located on the left side (left bottom).

Close-up of the volume control showing the 6 steps marked from loud to soft. The level is shown in the loudest position.

The earphone could be attached to a telescoping handle (shown in the extended position) and held to the ear as needed.

Note that later versions of this same model did not use screws, but were just a press-fit to hold them.
 

Instruction tag attached to a similar key reads, "Whenever you want to change the cord it is easy to disconnect it from your Acousticon.

Use this little screw-driver to loosen the four little screws that hold the four plugs—you will find two of these screws on the back of the ear-piece, and the other two in one of the openings in the front of the transmitter case.

Don't take the screws all the way out. Just loosen them enough to let the cord plugs come out.

Dictograph Products Corporation"

Here is a copy of an early manual explaining how to use early Acousticon carbon hearing aids--SRA, SRB, SRD and the Multi. It was printed after 1918, probably around 1920.