My wife's aunt was telling me about her first hearing aid. I was curious as to what type of batteries it used. I wasn't expecting her to say "high & low tension"!
A quick search reveals that there were indeed valve hearing aids around in the 50s
Tim
My oldest aunt on my mother's side had one in the '50s. I can remember it whistling away.
I can just remember using valve radio mics. These days, a *far* better performing one is a fraction of the size of the battery powering the valve one.
In message , Tim Downie writes
How fascinating! Tim, look here :
There is. Popliteal fossa.
Tim
I took one apart a couple of years ago.
It had little valves in it. I think they were called "Acorn valves" or some such.
Fairly simple circuit but did the job. Batteries were a back pack thing. :))
Tim
curious, my
heaters and very long and thin
AWEM
Didn't some car radios use valves like that too? And certainly the Russians were using miniature valves extensively in their military avionics until relatively recently. Apart from their lack of availability of semiconductors, valves were far more likely to survive the electronic effects of a nuclear blast.
Rob
Didn't some car radios use valves like that too? And certainly the Russians were using miniature valves extensively in their military avionics until relatively recently. Apart from their lack of availability of semiconductors, valves were far more likely to survive the electronic effects of a nuclear blast.
Rob
Semiconductors are very suceptable to EMP (electro magnetic pulse) which is a nuclear blast side effect. Valves are immune with the exception of the heaters - so emp proof valves run at lower voltages and higher currents on their heaters to be more robust, but also less effecient.
AWEM
Err, no! They were called hearing aid valves, oddly enough. Miniature things with wire leadouts, made by Hivac and Mullard/Philips. They would have been directly heated and designed to minimise the filament current (like the B7G 1.4-volt battery valves that many here will remember from portable radios of the pre-transistor era).
Acorn valves [1] were developed for VHF/UHF use, they were somewhat larger and had indirectly heated cathodes with 6.3 V heaters - much too thirsty to run from those old hearing aid batteries.
[1]
Indeed. I keep seeing things on the www that I thought I'd never see again. My grandmother had a hearing aid in the 50s, very like the OL15B, though ISTR the unit was flesh coloured.
John
I my case though, I was referring to the fact that Graeme quoted the same URL I had already posted!
Tim
In message , Tim Downie writes
Did I ???
Sorry, Tim :-)
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