[GreenKeys] TDD Frequencies

Thu Jun 4 02:50:10 EDT 2026

    This thread has me completely confused. Here are a couple of items 
confusing me:
1, Telephone Handset: this is usually the term for the part of an old 
fashioned telephone one picks up and holds in one's hands. It consists 
of a microphone and an earphone. The rest of the telephone is in a box 
of some sort. Somehow I think you mean something else. If I am right 
perhaps you can find a more exact term for it.
    One could connect an old type telephone for audio via the earphone 
both for receiving and sending. There are better ways of doing this.
2, Coupler: This is usually meant to refer to an acoustic coupler for 
both sending and receiving over a telephone without making an electrical 
contact with it. Couplers were used in the days when the Bell System 
absolutely forbade direct connections to phones. For instance, for 
connecting the phone to a ham rig for "phone patches".  With care the 
system works. There were also couplers that worked magnetically by 
coupling to the transformer inside the telephone. Another way to avoid a 
direct electrical connection to the phone.
    Somehow I don't think this is what you mean.
    Converter: sometimes used to refer to the decoder that converts 
audio tones to the direct current pulses used to operate the teletype 
machine.
    A converter works by sensing either audio tones or sometimes RF 
tones (as from the IF of a receiver) and converting them to the DC 
pulses needed to work the machine.
     A converter can also be made for transmitting, where it takes the 
on-off DC keying from the Teletype and converts it to either audio tones 
or to shifting the RF carrier.
     The most common shift of frequency these days is 170Hz but in the 
past 850 Hz was more common. Typical audio frequencies were 2125Hz and 
2975Hz (850 Hz), for narrower shift 2125Hz remained the lower frequency.
     Since the term TDD has been mentioned, it is another point of 
confusion. TDD are not the frequency shift tones mentioned above but 
rather tones used for transmitting Text. It is possible this whole 
discussion is about how to convert Text to TTY, in which case my whole 
post is irrelevant.
     There are many systems of tones used in communications, forinstance 
DTMF, the familiar dual tones used for sending direct dialing numbers.
     As far as my understanding of this thread it would be helpful to 
have some definitions of just what is being discussed.
     I am including a couple of links to the Navy Communications Page, 
which has a treasure of literature on it.
<https://www.navy-radio.com/rtty/ratt-5609.htm>
and the main page at:<https://www.navy-radio.com/rtty.htm>

On 6/3/2026 10:52 PM, Gavin Wuchter via GreenKeys 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 <mailto:greenkeys at mailman.qth.net>> wrote:
> 
>     __ __
> 
>     Ooops: manual states Mark/Space as 1400/1800.____
> 
>     __ __
> 
>     Close, but no guitar…____
> 
>     __ __
> 
>     __ __
> 
>     Cheerz____
> 
>     John____
> 
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