[GreenKeys] Modern Gadgets

[Jack]

I just got a new NEXTEL phone, Model i90c, and was
surprised to find that it has an option for using TTY devices
(for the deaf). It even has a menu setting for 45.45 or 50 baud!
They advise using 50 baud for "international" TTY calls.

There's a small jack on the top which is an audio interface
for a headset, handsfree, etc. It is also the interface for the
TTY device. So, I am assuming it takes the AFSK from the
TTY unit and converts it to an analog modem at the
switching center which is compatible to other TTY devices
and then converts the other way for the mobile to receive
the TTY signal.
.
The typical use of a cell phone for "switched data" actually
converts the proprietary signal from the phone into a
standard ASCII bitstream and sends it through a modem
pool (a rack full of shared modems) which is 
essentially equivalent to the modem in a PC.
That way the mobile user looks like any other analog
modem connection to the "other end".

How that for backward compatibility?

73,
Jack WA2HWJ

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