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uk.tech.digital-tv (Digital TV - General) (uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

Induction loops

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Old March 1st 18, 01:57 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,448
Default Induction loops

On 28/02/2018 19:16, Terry Casey wrote:

Way back in the mid 60s, when all the telephones were owned by
the GPO and you were forbidden to touch or attach anything to
any part of the system, someone came up with a little cheat to
turn any normal GPO telephone into a loudspeaking telephone
without breaking the rules!

It looked like one of the little Japanese pocket radios that
were so popular at the time - in fact, it used the same case!

Inside were a battery, loudspeaker and amplifier but no radio
section. Instead, there was an induction coil with a rubber
sucker on it with a length of wire coiled up beside it.

Operation was simple - remove the induction coil and hold it
behind the 'phone, lift the receiver and move the coil around
for maximum volume of the dial tone. Then give the sucker a
lick and stick it on the phone.

Blimey that brings back memories! As a teenager I must have seen an
article in a mag because I used a coil from an ex-army item (we used to
steal from a local yard that was full of the stuff) and connected it to
(I think) the gram socket of a radio. It worked fine as a telephone

Not long afterwards we had a visit from a woman clutching a
leaflet from the RNID about installing an induction loop
connected to the TV - her son was very deaf, she said, and
relied on a hearing aid.

All TV's at the time had one side of the mains connected to
the chassis so, for safety's sake, we supplied a 1:1 speaker
isolating transformer,

I didn't know or care about safety so when grandma complained that
people on the telly were whispering I connected a pair of headphones
(headphones, wireless, tank crew, MkIV) to the speaker terminals with no
isolation. I must have included a plug/socket because gran took to
wearing the phones at all times, with the flex in her pinny pocket. She
said they helped her reumatics.


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