[GreenKeys] TDD Frequencies

[hwhall@aol.com]

You cannot simply slow the audio playback down because that will stretch the pulse widths, effectively changing the keying speed & creating more problems.
Maybe study the phone interface circuit & maybe there's something that can be tweaked to change the tones it detects.
If you're up for building a circuit, because you're not copying noisy & fading tones off-the-air, a demodulator can be pretty simple. A little PLL IC & a keying transistor may be all that's required.

Wayne
WB4OGM

On Wednesday, June 3, 2026 at 11:53:11 PM MDT, Gavin Wuchter via GreenKeys <greenkeys at mailman.qth.net> wrote: 

Welp lol, now I guess my question is does anyone know of a software modem or other itty thing that can output the original APCOM/PhoneType 1400/1800 Hz Baudot tones?


Or in theory something that can slow down the audio to be slight lower pitch/frequency?

Just a thought trying to be somewhat cost effective for the equipment I already have. 

Thank you for your help in the search!
- Gavin
On Thu, Jun 4, 2026 at 12:43 AM John Lawson via GreenKeys <greenkeys at mailman.qth.net> wrote:
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> Ooops: manual states Mark/Space as 1400/1800.
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> Close, but no guitar…
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> Cheerz
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> John
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