I4BTEL(4) MidnightBSD Kernel Interfaces Manual I4BTEL(4)

NAME

i4btel — isdn4bsd ISDN B-channel telephony interface driver

SYNOPSIS

device "i4btel" [count]

DESCRIPTION

The i4btel driver provides an interface to the ISDN B-channel for telephony applications and is currently used by the isdnd(8) for answering machine support. The driver is part of the isdn4bsd package.

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.

Functionality zero is the usual telephony data stream i/o driver.

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 i4b_tel_ioctl.h and the isdnphone(8) utility.

The telephony data stream comes out of the line in a bit-reversed format, so the i4btel driver does the bit-reversion process in any case.

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 isdntelctl(8) utility.

The driver is able to process several ioctl’s:

I4B_TEL_GETAUDIOFMT

get currently used audio format conversion.

I4B_TEL_SETAUDIOFMT

set currently used audio format conversion.

I4B_TEL_EMPTYINPUTQUEUE

clear the input queue.

For the I4B_TEL_GETAUDIOFMT and I4B_TEL_SETAUDIOFMT, the following parameters are available:

CVT_NONE

do no A-law/u-law audio format conversion. The conversion path looks like this:

USER <--> bitreversing <--> ISDN-line

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 read(2) conversion path looks like this:

USER <-- u-law/A-law <-- bitreversing <-- ISDN-line

and the write(2) conversion path looks like this:

USER --> u-law/A-law --> bitreversing --> ISDN-line

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 read(2) conversion path looks like this:

USER <-- A-law/u-law <-- bitreversing <-- ISDN-line

and the write(2) conversion path looks like this:

USER --> A-law/u-law --> bitreversing --> ISDN-line

SEE ALSO

g711conv(1), isdnd.rc(5), isdnd(8), isdnphone(8), isdntelctl(8)

STANDARDS

A-Law and u-Law are specified in ITU Recommendation G.711.

AUTHORS

The i4btel device driver and this manpage were written by Hellmuth Michaelis 〈hm@FreeBSD.org〉.

MidnightBSD 0.3 July 28, 2002 MidnightBSD 0.3