NAME
isdntel —
ISDN B-channel telephony
interface driver
SYNOPSIS
pseudo-device isdntel count
DESCRIPTION
The
isdntel driver provides an interface to the 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 driver's minor number are 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
/usr/include/netisdn/i4b_tel_ioctl.h and the
isdntel(8) utility.
The telephony data stream comes out of the line in a bit-reversed format, so the
isdntel driver does the bit-reversion process in any case.
Additionally, the user can specify to do A-law to mu-law, mu-law to A-law or no
conversion at all in the
isdntel 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/mu-law audio format conversion. The conversion
path looks like this:
USER <--> bitreversing <--> ISDN-line
- CVT_ALAW2ULAW
- set audio format conversion to do an audio conversion from
A-law (on the ISDN line) to mu-law (in the userland). The
read(2) conversion path looks
like this:
USER <-- mu-law/A-law <-- bitreversing <-- ISDN-line
and the write(2) conversion
path looks like this:
USER --> mu-law/A-law --> bitreversing --> ISDN-line
- CVT_ULAW2ALAW
- set audio format conversion to do an audio conversion from
mu-law (on the ISDN line) to A-law (in the userland). The
read(2) conversion path looks
like this:
USER <-- A-law/mu-law <-- bitreversing <-- ISDN-line
and the write(2) conversion
path looks like this:
USER --> A-law/mu-law --> bitreversing --> ISDN-line
SEE ALSO
isdnd.rc(5),
isdnd(8),
isdntel(8),
isdntelctl(8)
STANDARDS
A-law and mu-law are specified in ITU Recommendation G.711.
AUTHORS
The
isdntel device driver and this man page were written by
Hellmuth Michaelis
<
hm@kts.org>.