Radioear B-7B Carbon Hearing Aid
The Radioear B-7B carbon hearing aid was manufactured by E. A. Myers &
Sons, Ltd. of Pittsburg, PA in 1931.
The B-7B transmitter (microphone), shown in the pictures, measured
3⅜" in diameter, while the B-7A (a similar model) was slightly larger
measuring 3˝” in diameter.
The carbon transmitter (microphone) plugged onto a battery case that held two “C”
size batteries, or it could be plugged directly onto a Radioear battery.
The operating voltage was 3 or 4˝ volts depending upon the amount of power
required for a given hearing loss.
A small black miniature receiver, onto which an
ear mold was clipped, plugged into the transmitter.
Typically, the Model B-7A came with an air conduction receiver, while the
Model B-7B came equipped with a bone conduction receiver (although here
the B-7B is shown with the air conduction receiver).
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The front of the Radioear B-7B transmitter (microphone) showing the
on-off switch/rheostat volume control (left). It is in the off position.
Down all the way would be the loudest volume. On the right side is a
"Tel/Voice" switch. Moving the Tel-Voice switch to the “Tel” position opened up
the 5 screened
holes in the centre of the transmitter so that a telephone receiver
could be held directly against the carbon transmitter.
When in the “Voice”
position, the sound entered the carbon transmitter through the six slots
located around the circumference of the transmitter.
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