ISDNTEL(4)              NetBSD Kernel Interfaces Manual             ISDNTEL(4)

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 param-
     eters 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>.

NetBSD 5.0_STABLE               April 21, 1999               NetBSD 5.0_STABLE
