EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: eti on December 05, 2022, 07:31:50 am
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Have you heard of those?
I used to make phone taps, fm telephone bugs and beige boxes (before the internet and it’s “let me show you how to X” mindset - it’s all incredibly simple and is logical profession when you have to work things out; that’s what develops one’s mind!) back in the 90s.
Also I looked into “infinity transmitters”. A chap here in England used to make an INCREDIBLY impressive range of these - minuscule black blocks which had all the clever stuff potted inside, brought out onto 2 turned gold pin sockets which were sitting flush with the surface of the carefully sanded flat black potting compound. The construction alone was a work of art. I wish I could remember his name.
I’d call him at home (we never met) and he’d tell me the DTMF code he’d set into the demo unit; he’d tell me he was going to hang up and that I should wait X seconds and then enter the code, which I did, and I’d then hear VERY amplified room audio from his end.
Google ”Infinity transmitter” - but I’d caution against using one!!
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I know that, when the old phones used potted modules for the electronics, there were a good number of those that were made to look alike to the original GPO potted blocks, to be installed in the phones servicing certain locations. Identical box and potting (of course, seeing as the builders had the way to get the right potting boxes, potting compound, silkscreen prints and wires in the potting), and often the only way to tell would be an extra wire to connect the other end of the hook switch, nominally there as "contact interference suppressor" connection.
Of course when installed the lines also were monitored...... But this allowed the room to be listened to as well.