🚀 go-pugleaf

mikel@networx.com (Mike Lempriere) says:
>I'm building a TDD (Telecommunications Device for the Deaf) interface
>for my IBM PC.
>
>Several years ago, I built a phone line coupler, and analysed TDD signals
>by means of timing loops on my Apple ][.  From this, I determined a bunch
>of stuff, but due to the nature of my testing mechanism, I'd like
>confirmation of these details:
>
>a)  TDD baud rate is 45.5 baud (sheesh).
>b)  Basic carrier (space tone) is 1400Hz.
>c)  Mark frequency is 1800Hz.

Mark and space are inverted from the more familiar computer modems.  If
you hack an old computer modem, you will need to invert the RS-232 data
or you will get garbage.

>d)  There is always 1 mark start bit.
>e)  There are 5 data bits.
>f)  There is always 1 space stop bit.  (Would 1.5 or 2 work too?)

g)  The carrier (but not the connection) must drop ~1 second after the
    last character is sent.
h)  Weitbrecht (TDD) modems are half-duplex.
-- 
  Bob Billson, KC2WZ                          | internet: bob@kc2wz.bubble.org
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