The TA’s are connected to national German ISDN (1TR6) or Euro-ISDN. The host side is a standard serial port with an AT-command set, letting them look like a conventional modem. Therefore they are often (wrongly) called ’ISDN modems’.
It is strongly recommended to feed them with 115k2 bps, else only V.110 (38k4 bps) is available. Configuration may differ slightly, depending on which of those Elinks is used, wether it is connected to Euro-ISDN or 1TR6 and last but not least they are still under developement, so you’re on your own with that.
ISDN generally supports two nice features: first it is now possible to
check callers number, which may be used to identify callers, second ist
the charge service, where it is possible to request the amount of charge
units for the call. For mgetty the second one is only from minor interest,
but the first one is. The opposite phone number will be shown with the
command AT\O. If a call comes in, AT\OA will answer the
call, display caller’s id in a ’digit only’ (e.g. ‘04419808550’) form
and then print out the CONNECT-String.
To enable mgetty to utilize this, the "get caller ID" sequence must be set up accordingly and the ‘CND’ feature must be enabled:
Use get-cnd-chat "" AT\\O OK in mgetty.config, and make
sure that #define CNDFILE "…/dialin.config" at the
end of policy.h is enabled.
If you only want to grab the phone
number and not check it against dialin.config, you can try playing
with something like answer-chat "" AT\\OA CONNECT \c \r
in mgetty.config.
Having a glance at the output of AT I4-output of the Elink, it looks
as if it is able to support Fax-Service too, but there is no hint in the
manual. So mgetty will likely put itself into data-only mode. (I got some
information from the Elink people that some of the Elinks have a data/fax
analog modem built in, which should work nicely with the fax part of
mgetty, but I didn’t try yet.)
(Thanks to Ulrich Tieman, lord@olis.north.de, for this section. Don’t ask me, ask him if you use an ELINK)