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Old 23rd Oct 2023, 11:25 am   #1
TonyDuell
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Default What is it?

Does anyone know what this unit is?

The photos show the unit with the carrying case, the internals (the empty space is for a PP3 battery which gives an idea of the size of the unit) and the component side of the PCB

I've also attached a reverse-engineered circuit diagram.

It generates a 1800Hz tone when you press the button. The frequency is determined by a Murata resonator and is therefore quite accurate.

It's clearly a commercial unit (custom moulded case, the carrying case) but there's no maker's name anywhere on it. The transistors are Japanese 2SC... types.

One suggestion is that it's a simple remote control for a telephone answering machine, but does anyone know for sure?
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File Type: pdf Tone_Signal_1800Hz.pdf (375.2 KB, 52 views)
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Old 23rd Oct 2023, 12:18 pm   #2
Nickthedentist
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Default Re: What is it?

I think the answering machine interrogator is extremely likely, or some other application which relies on a tone being sent down the phone.
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Old 23rd Oct 2023, 1:49 pm   #3
G6Tanuki
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Default Re: What is it?

Some Continental amateur radio repeaters needed an 1800Hz toneburst in place of the then-UK-standard 1750Hz.

I wonder if this 'thing' could have been sold to allow UK hams with a 1750Hz toneburst to access Continental repeaters when travelling?
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Old 27th Oct 2023, 5:31 pm   #4
Graham G3ZVT
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Default Re: What is it?

Quote:
Originally Posted by Nickthedentist View Post
I think the answering machine interrogator is extremely likely, or some other application which relies on a tone being sent down the phone.
Agreed.
Perhaps from this TAM I have here


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although mine is 1900Hz

Incidentally the frequency generating device in the handset is not a crystal, it's a mechanical tuning fork resonator. There is a similar one in my Trio 2200G transceiver for 1750Hz
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