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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 3rd Jul 2022, 8:04 pm   #1
DMcMahon
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Default What is this device - a microphone ?

I think it came with a bunch of bits with a Sony Tape Recorder.

It is small (25mm x 20mm) and the flexible rubber cup at the front acts like a suction cup and will easily stick to a flat surface.

It measures around 750 Ohms / 273mH

Initially thought maybe a microphone but now not so sure because of the suction cup, maybe a transducer for measuring something or accelerometer etc.

Only marking on it is "Japan" on the mini jack connector body.

Does anybody recognise it ?

David
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Old 3rd Jul 2022, 8:11 pm   #2
Dave Moll
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Default Re: What is this device - a microphone ?

It looks like a telephone pickup - for connecting an external amplifier or recorder to hear or record a call.

It picks up the magnetic field either from the induction coil or the earpiece.
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Old 3rd Jul 2022, 8:12 pm   #3
ms660
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Default Re: What is this device - a microphone ?

Telephone pickup.

EDIT: Post crossed.

Lawrence.
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Old 3rd Jul 2022, 8:15 pm   #4
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Default Re: What is this device - a microphone ?

You stuck it onto the handset of your landline to make a recording of the conversation, David. I used one in the seventies when my mate Frank used to read the risque jokes from the local Rag Mag! The next day they were all around the school.
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Last edited by Kentode; 3rd Jul 2022 at 8:16 pm. Reason: Post triple crossed!
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Old 3rd Jul 2022, 8:31 pm   #5
The Philpott
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Default Re: What is this device - a microphone ?

I thought i recognised it- as seen in episodes of The Sweeney, The Professionals, Smiley's People, etc!

Dave
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Old 3rd Jul 2022, 8:34 pm   #6
DMcMahon
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Default Re: What is this device - a microphone ?

Well done everybody, it makes sense now.

David
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Old 3rd Jul 2022, 10:19 pm   #7
McMurdo
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Default Re: What is this device - a microphone ?

TV companies sometimes used them to record a conversation with some rogue trader back in the day, often held on with gaffer tape
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Old 4th Jul 2022, 7:39 am   #8
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Default Re: What is this device - a microphone ?

If I remember it only worked with certain older phones. J.
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Old 4th Jul 2022, 10:28 am   #9
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Default Re: What is this device - a microphone ?

Yes, presumably ones with quite a lot of stray magnetic field from the receiver (earpiece).
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Old 4th Jul 2022, 10:37 am   #10
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Default Re: What is this device - a microphone ?

I found that on the old 706/746 phones the best place to attach the coil was on the back of the phone itself alongside the cable entry.

By coincidence a dealer friend of mine gave me one just the other week, again he didn’t know what it was.

Peter
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Old 4th Jul 2022, 11:36 am   #11
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Default Re: What is this device - a microphone ?

That's clever, it must be picking up the field from the ASTIC.
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Old 4th Jul 2022, 12:38 pm   #12
Dave Moll
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Default Re: What is this device - a microphone ?

The advantage of using the induction coil is that you don't have a second cable attached to the handset - especially if you're relying on the suction cup.
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Old 4th Jul 2022, 12:59 pm   #13
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Default Re: What is this device - a microphone ?

They work well with the open-core ASTICs in Telephone 232's and the like, not always as well with the later ASTICs used in the 700 series. But they were always worth trying.

Another (unofficial) use for them was to pick up the stray field round the audio output transformer in an AC/DC radio. Here of course you could try the pickup coil close to the transfomer inside the set. While the quality wasn't great, it had the advantage ove the other method of puting the tape recorder microphone in front of the radio speaker that the pickup coil was not affected by other noises in the room.
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