CC: clewis@ferret.ocunix.on.ca (Chris Lewis)

Like a smarter `getty'.  getty is the program that manages the
first step of the login procedure on a Unix computer; when used
with a modem, it watches for an incoming call and (ordinarily)
prints the "login:" prompt (and reads the username, and passes off
to "login").

Unlike traditional versions of getty or uugetty, which will put a
modem into auto-answer mode, mgetty does not.  When an incoming call
occurs, mgetty sees the "RING"s when they occur.  When they do occur,
mgetty tells the modem to answer, and the modem will tell mgetty what
kind of connection happens.  If it is FAX, mgetty will receive the
FAX.  If data, mgetty prompts for a userid, then hands the open line
off to login for a normal data login.

Note that it's the modem's job to distinguish a FAX call from a data
call.  Not all fax modems can do this, and if yours _can't_ there is no way
for mgetty to do this for it.  mgetty can be used with modems that
cannot distinguish a fax call from a data call, but you must tell it
ahead of time what type of call to expect.

mgetty is also configurable to select programs other than login for
special connections (eg: uucico, fido or other programs) depending
on the login userid.

mgetty also supports caller-id and can deny connections based on
originating telephone number.

vgetty is an extension to mgetty that works with voice-capable
modems to provide additional call-handling capabilities.  When the
modem reports a RING, vgetty has the modem pick up the line and
play a voice message (the greeting).  If the modem detects a data or
fax calling tone, it reports this back to vgetty with special codes
(DLE-sequences) which causes vgetty to switch to either mode. Else
voice mode is used.

If instead the modem hears nothing following the greeting (a
certain level of silence that continues for a certain number of
seconds) it assumes the caller is a data modem and attempts a data
connection.

vgetty implements the normal answering-machine functions of
remote message playback as well; its operation is driven from shell
scripts, so you can extend it to a full voice-mail jail if you
wish.  (This description of voice modem behavior applies to the
ZyXELs; I [steve@work.bellingham.wa.us] assume other voice modems
are similar.)

For an example on how a voice mail system looks like, there is the
voice_mail.sh script in voice/scripts from Marc Schaefer. Since the voice
shell is independent of the real modem hardware, it works on all supported
modems, not just ZyXELs. The hardware drivers hide the modem specific stuff,
so that the voice shell can provide a general interface that is completely
modem independant. Of course the reliability of the whole systems relies on
the reliability of the used voice modem. And there are quite notably
differences between different modems.

vgetty is intended for people who want to share a phone line for
data and voice use, with the main focus being voice calls. It is
*NOT* intended for a dialup system that occasionally gets a voice
call, since some modems are confused by hearing a recorded voice
message and won't connect.

If you have distinctive ring, you still can have one line, but vgetty can
detect the type of the call from the RING message and switch directly
to data/fax mode. In countries where distinctive ring is supported,
you can have dialup and voice on the same line without problems.

Voice extensions were originally written by Klaus Weidner
(klaus@snarc.greenie.muc.de) but are now maintained by Marc Eberhard
(Marc.Eberhard@Uni-Duesseldorf.DE).  Direct questions about them to that
address.

More from the distribution (some edits):

This is what you can do with `sendfax' if you have a standard class
2.0 or 2 fax modem:

* send faxes directly or using shell scripts (easily integrated into
  other applications).

* do "fax polling", this means you can call the weather station and
  get them to send you a fax containing the current weather map.
  (Not all modem manufacturers implement this feature in their
  modems!)

* create a "fax queue", outgoing faxes get sent automatically, the
  user is informed by mail about the result.

`mgetty' allows you to use a single modem line for receiving calls
and dialing out.

* `mgetty' knows about "smart" modems, and will make sure that the
  modem is always in a defined state (specific modem initialization
  possible)

* Incoming calls are answered manually (`RING' -> `ATA' ->
  `CONNECT') instead of using auto-answer (`ATS0=1'), this way the
  modem won't pick up the phone when the machine is down or logins
  are not allowed.

* mgetty completely replaces getty and/or uugetty.  Like uugetty,
  supports lock files in a fashion compatible with almost all known
  versions of UUCP (HDB/BNU, SVR4, V7, Taylor in various flavours).
  uugetty has some features mgetty doesn't support; see "How does
  mgetty differ from uugetty?" below.

* mgetty supports System V style gettydefs terminal configurations.
 
* mgetty can receive class 2 faxes (if your modem supports it).

* mgetty knows about incoming FidoNet calls.

* mgetty has extensive logging / debugging features

* do "fax poll sending", that is, you can setup your machine as fax
  poll server, to send some fax pages to "fax poll" callers. (Send
  informations about your system, the current wheather map, ...). Be
  warned, even less modems support this feature.

* mgetty can selectively refuse calls based upon CallerID, if your
  modem supports it, and you're subscribed to the service. CallerID
  is also logged.

* mgetty has facilities to allow you to refuse incoming FAXes when
  available disk space is low.

* mgetty knows about incoming PPP calls, and can hand them off
  to the PPP-daemon, without requiring a login/password sequence. This
  feature is also known as AutoPPP

vgetty inherits all of mgettys features, and offers some additional
ones:

* behaves like a normal answering machine for human callers

* automatic fax reception when a T.30 calling tone is detected

* If the caller isn't a human or fax, a data connect is attempted,
  if this is successful, the caller will get a normal login

* does not interfere with dialouts

* remote playback of messages via a DTMF code

* toll saver -- if there are new messages, pick up the phone
  earlier, this way you can hang up in time to avoid a useless call

* message light - the autoanswer LED of your modem (if it has one)
  is turned on if there are new messages

* easy playback - on some modems, you can play back the new messages
  just by pressing DATA/VOICE

* using a speech synthesizer is possible - add the date and time to 
  messages (not included by default). The scripts show how to use a 
  speech synthesizer like rsynth, but it is not included in the 
  package. To use this feature, you need a voice modem for that; 
  a converter from the pvf format to the rmd (raw modem data) format
  exists. This is not true for all supported modems.

* voice conversion utilities - play messages on /dev/audio
  (Not for all supported modems, some voice modems use a proprietary
  format)