Otarion L10 "Listener"

The Otarion Model L10 "Listener" eyeglass hearing aid was manufactured by Otarion Electronics, Inc. of Chicago, IL.

The Otarion Model L10 was introduced on December 9, 1954 and went on sale in January 1955. It was probably the first commercially-made all-transistor eyeglass hearing aid in the world.

(Note: Akumed MBH of Germany had come out with a 2 vacuum tube & 1 transistor eyeglass hearing aid in 1954 (patented in 1952). This was likely the first commercially-made eyeglass hearing aid in the world. Another unique feature of this hearing aid was that the arms could not fold.)
 

This hearing aid weighed 2.1 oz. (58 g) without the battery.

It used discrete components, and as such, needed both sides of the eyeglass frames to house all the electronics—hence its "fat" arms.

Furthermore, since the electronics filled both arms, only one ear could be aided. In the model shown at the right, it provided amplification for the left ear.

Note the ear mold attached to the left arm.

 In addition, since the microphone and receiver were on opposite sides of the eyeglasses, this effectively made this aid function as a CROS, (Contralateral Routing of Sound) hearing aid. The hearing aid picked up the sound from one side of your head and you heard it in the opposite (contralateral) ear.

The battery door just slid up in two tiny grooves.

The Otarion L10 "Listener" used a No. 625 battery.

Close-up view of the inside of the left arm of the Otarion Model L10 "Listener" eyeglass hearing aid showing the battery door half shut.

This was needed since both arms housed the electronics. As a result, there needed to be a way of connecting both sides with wires. The way they did it was to run 2 wires along both arms to pins at the front and run hidden wires across the top of the eyeglass frames (as shown).

In order not to have wires visible at the corner hinges, Otarion came up with an ingenious method for connecting the wires in the arms and the eyeglass frame together.

 Note the two pins sticking off the end of the arm. These pins automatically made contact with the "plates" (right) when the arms were opened up so you could put the eyeglasses on and broke contact  (shown) when the arms were folded. In this way the electrical signals were transferred from one side to the other. (Both arms had the same arrangement.)

You had to keep the ends of the pins and the "plates" clean or they would soon corrode and the hearing aid would cease working, or cease working properly.

Note: there was no on-off switch on the volume control or elsewhere as none was needed. Simply folding the eyeglass arms broke the contacts at the hinges and prevented any current from flowing.

At the right is an advertising invitation for the Otarion Model L10 "Listener" eyeglass hearing aid dated April 1955.

Here is a copy of the slick 4-page brochure for the Otarion Model L10 "Listener" eyeglass hearing aid to entice people to purchase it. Notice the stress on invisibility—just as is done today.

The Otarion Model L10 "Listener" eyeglass hearing aid in its original case.

The original case of the Otarion Model L10 "Listener" eyeglass hearing aid.