README

 app_softmodem.c - V.21/V.22/V.23 modem for Asterisk
===============================================================================

	This Asterisk application provides a softmodem for Asterisk. It supports
	the FSK standards V.23, V.21 and Bell 103, but also V.22 and V.22bis.
	Byte-size, number of stopbits and bitordering is configurable.
	A TCP connection comparable to a Telnet session is established to the
	host specified.


 Dependencies and Installation
-------------------------------------------------------------------------------

	app_softmodem.c depends on the spandsp library
	(http://www.soft-switch.org/).

	It is tested and working with Asterisk 13t.

	To compile put app_softmodem.c in the apps/ dir of your Asterisk source.
	Compile with 'make apps'.

	To use do a 'make install' on your asterisk source or copy
	apps/app_softmodem.so into your asterisk module directory
	(/lib/asterisk/mosules).


 Dialplan
-------------------------------------------------------------------------------

	exten => btx,1,Answer()
	exten => btx,n,Softmodem(host, port, options)
	exten => btx,n,Hangup()

	Without any arguments the application acts as a V.23 modem and connects to a
	Telnet server (port 23) on localhost.

	Options are:
		r(...): rx cutoff (dBi, float, default: -35)
		t(...): tx power (dBi, float, default: -28)
		v(...): modem version (default: V23):
				V21        - 300/300 baud
				V23        - 1200/75 baud
				Bell103    - 300/300 baud
				V22        - 1200/1200 baud
				V22bis     - 2400/2400 baud
		l or m: least or most significant bit first (default: m)
		d(...): amount of data bits (5-8, default: 8)
		s(...): amount of stop bits (1-2, default: 1)
		e or o: add even or odd parity bit
		u:      Send Ulm Relay Protocol header to Telnet server
		n:      Send NULL-Byte to modem after carrier detection (Btx specific)

	To act as a "Btx Vermittlungsstelle" (German videotex system) using V.23, 8 data bits, 1 stop bit and sending a NULL byte upon carrier detection and connecting to a "twistedUlm" server on port 8289 (thus sending the ULM header):

	exten => 190,1,Softmodem(localhost, 8289, v(V23)ld(8)s(1)un)

	To accept calls fom UK Prestel terminals, using V.23, 7 data bits, Even parity, 1 stop bit -

	exten => 618,n,Softmodem(localhost, 6502, v(V23),ld(7)es(1)t(-8))

	The modem seems to work fine with VOIP as long as you use a codec like G.711
	(alaw/ulaw). Please deactivate any echo cancellation you might use.



 Btx, the Ulm Relay Protocol, general description of operation
-------------------------------------------------------------------------------

	After the softmodem picks up the line a TCP connection to the specified host
	and port is established, the call is dropped when this wasn't successfull.

	When the "n" option is specified a NULL byte is send to the caller upon the detection of a carrier signal from the caller. The Btx system in Germany did this to request the caller's identification.

	With the "u" option specified a header is send to the TCP server at this
	point. The header consists of some "name: value" pairs, separated by a CR+LF newline, terminated	by a double newline.

	At the moment this header looks like (for V.23):
		Version: 1
		TXspeed: 120
		RXspeed: 7.5
	Speeds are in bytes-per-second and may be used by the server to estimate
	the length of the transmission.

	After the header all data received from the terminal is put onto the socket
	and all data received from the socket is put on the line.

	The line is hung up when the server drops the connection, just as the
	connection to the server is dropped when the line is hung up.

	You find my "Ulm Relay Protocol" server here:
	http://github.com/proquar/twistedUlm
	It sends CEPT T/CD 6-1 encoded data, which it retrieves from a webserver,
	to the terminal and provides the characteristic BTX look-and-feel.

	You may also be interested in:
		http://runningserver.com/?page=runningserver.content.thelab.bildschirmtrix
	And you find a description of BTX MarkupLanguage here:
		http://runningserver.com/?page=runningserver.content.thelab.mikropad


 Authors
-------------------------------------------------------------------------------

	Christian Groeger <code@proquari.at>

	Based on code by:
	Dmitry Andrianov <asterisk@dima.spb.ru>
	Steve Underwood <steveu@coppice.org>






===============================================================================

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  14. Revised Versions of this License.

  The Free Software Foundation may publish revised and/or new versions of
the GNU General Public License from time to time.  Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.

  Each version is given a distinguishing version number.  If the
Program specifies that a certain numbered version of the GNU General
Public License "or any later version" applies to it, you have the
option of following the terms and conditions either of that numbered
version or of any later version published by the Free Software
Foundation.  If the Program does not specify a version number of the
GNU General Public License, you may choose any version ever published
by the Free Software Foundation.

  If the Program specifies that a proxy can decide which future
versions of the GNU General Public License can be used, that proxy's
public statement of acceptance of a version permanently authorizes you
to choose that version for the Program.

  Later license versions may give you additional or different
permissions.  However, no additional obligations are imposed on any
author or copyright holder as a result of your choosing to follow a
later version.

  15. Disclaimer of Warranty.

  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

  16. Limitation of Liability.

  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.

  17. Interpretation of Sections 15 and 16.

  If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely approximates
an absolute waiver of all civil liability in connection with the
Program, unless a warranty or assumption of liability accompanies a
copy of the Program in return for a fee.

                     END OF TERMS AND CONDITIONS

            How to Apply These Terms to Your New Programs

  If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.

  To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.

    <one line to give the program's name and a brief idea of what it does.>
    Copyright (C) <year>  <name of author>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

Also add information on how to contact you by electronic and paper mail.

  If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:

    <program>  Copyright (C) <year>  <name of author>
    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
    This is free software, and you are welcome to redistribute it
    under certain conditions; type `show c' for details.

The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License.  Of course, your program's commands
might be different; for a GUI interface, you would use an "about box".

  You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
<http://www.gnu.org/licenses/>.

  The GNU General Public License does not permit incorporating your program
into proprietary programs.  If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications with
the library.  If this is what you want to do, use the GNU Lesser General
Public License instead of this License.  But first, please read
<http://www.gnu.org/philosophy/why-not-lgpl.html>.