.\"
.\" Copyright (c) 1997, 1999 Hellmuth Michaelis. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"	$Id: i4btel.4,v 1.9 1999/12/13 22:11:55 hm Exp $
.\"
.\" $FreeBSD: src/usr.sbin/i4b/man/i4btel.4,v 1.8.2.6 2003/03/13 03:10:59 trhodes Exp $
.\" $DragonFly: src/usr.sbin/i4b/man/i4btel.4,v 1.4 2006/02/17 19:40:15 swildner Exp $
.\"
.\"	last edit-date: [Mon Dec 13 23:13:39 1999]
.\"
.Dd April 21, 1999
.Dt I4BTEL 4
.Os
.Sh NAME
.Nm i4btel
.Nd isdn4bsd ISDN B-channel telephony interface driver
.Sh FreeBSD SYNOPSIS
.Cd pseudo-device \&"i4btel\&" Op count
.Sh NetBSD SYNOPSIS
none
.Sh DESCRIPTION
The
.Nm
driver provides an interface to the B-channel for telephony applications
and is currently used by the
.Xr isdnd 8
for answering machine support. The driver is part of the isdn4bsd package.
.Pp
The lower six bits of the drivers's minor number is used to specify a
unit number, whereas the upper two bits specify a functionality.
.Pp
Functionality zero is the usual telephony data stream i/o driver.
.Pp
Functionality one is used to enable commands to dial out and hang up and
receive responses about the state of the dial out progress and status.
This commands may change in the future, for details see the file
.Em i4b_tel_ioctl.h
and the
.Xr isdnphone 8
utility.
.Pp
The telephony data stream comes out of the line in a bit-reversed format,
so the
.Nm
driver does the bit-reversion process in any case.
.Pp
Additionally, the user can specify to do A-law to u-law, u-law to A-law
or no conversion at all in the i4btel driver by using the
.Xr isdntelctl 8
utility.
.Pp
The driver is able to process several ioctl's:
.Pp
.Bl -tag -width Ds -compact -offset indent
.It Ar I4B_TEL_GETAUDIOFMT
get currently used audio format conversion.
.It Ar I4B_TEL_SETAUDIOFMT
set currently used audio format conversion.
.It Ar I4B_TEL_EMPTYINPUTQUEUE
clear the input queue.
.El
.Pp
For the I4B_TEL_GETAUDIOFMT and I4B_TEL_SETAUDIOFMT, the following
parameters are available:
.Pp
.Bl -tag -width Ds -compact -offset indent
.It Ar CVT_NONE
do no A-law/u-law audio format conversion.
The conversion path looks like this:
.Pp
USER <--> bitreversing <--> ISDN-line
.Pp
.It Ar CVT_ALAW2ULAW
set set audio format conversion to do an audio conversion from A-law
(on the ISDN line) to u-law (in the userland).
The
.Xr read 2
conversion path looks like this:
.Pp
USER <-- u-law/A-law <-- bitreversing <-- ISDN-line
.Pp
and the
.Xr write 2
conversion path looks like this:
.Pp
USER --> u-law/A-law --> bitreversing --> ISDN-line
.Pp
.It Ar CVT_ULAW2ALAW
set set audio format conversion to do an audio conversion from u-law
(on the ISDN line) to A-law (in the userland).
The
.Xr read 2
conversion path looks like this:
.Pp
USER <-- A-law/u-law <-- bitreversing <-- ISDN-line
.Pp
and the
.Xr write 2
conversion path looks like this:
.Pp
USER --> A-law/u-law --> bitreversing --> ISDN-line
.Pp
.El
.Sh SEE ALSO
.Xr g711conv 1 ,
.Xr isdnd.rc 5 ,
.Xr isdnd 8 ,
.Xr isdnphone 8 ,
.Xr isdntelctl 8
.Sh STANDARDS
A-Law and u-Law are specified in ITU Recommendation G.711.
.Sh AUTHORS
The
.Nm
device driver and this manpage were written by
.An Hellmuth Michaelis Aq hm@FreeBSD.org .