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34 .Nd isdn4bsd ISDN B-channel telephony interface driver
36 .Cd device \&"i4btel\&" Op count
40 driver provides an interface to the ISDN B-channel for telephony applications
41 and is currently used by the
43 for answering machine support.
44 The driver is part of the isdn4bsd package.
46 The lower six bits of the drivers's minor number is used to specify a
47 unit number, whereas the upper two bits specify a functionality.
49 Functionality zero is the usual telephony data stream i/o driver.
51 Functionality one is used to enable commands to dial out and hang up and
52 receive responses about the state of the dial out progress and status.
53 This commands may change in the future, for details see the file
59 The telephony data stream comes out of the line in a bit-reversed format,
62 driver does the bit-reversion process in any case.
64 Additionally, the user can specify to do A-law to u-law, u-law to A-law
65 or no conversion at all in the i4btel driver by using the
69 The driver is able to process several ioctl's:
71 .Bl -tag -width Ds -compact -offset indent
72 .It Ar I4B_TEL_GETAUDIOFMT
73 get currently used audio format conversion.
74 .It Ar I4B_TEL_SETAUDIOFMT
75 set currently used audio format conversion.
76 .It Ar I4B_TEL_EMPTYINPUTQUEUE
77 clear the input queue.
80 For the I4B_TEL_GETAUDIOFMT and I4B_TEL_SETAUDIOFMT, the following
81 parameters are available:
83 .Bl -tag -width Ds -compact -offset indent
85 do no A-law/u-law audio format conversion.
86 The conversion path looks like this:
88 USER <--> bitreversing <--> ISDN-line
91 set set audio format conversion to do an audio conversion from A-law
92 (on the ISDN line) to u-law (in the userland).
95 conversion path looks like this:
97 USER <-- u-law/A-law <-- bitreversing <-- ISDN-line
101 conversion path looks like this:
103 USER --> u-law/A-law --> bitreversing --> ISDN-line
106 set set audio format conversion to do an audio conversion from u-law
107 (on the ISDN line) to A-law (in the userland).
110 conversion path looks like this:
112 USER <-- A-law/u-law <-- bitreversing <-- ISDN-line
116 conversion path looks like this:
118 USER --> A-law/u-law --> bitreversing --> ISDN-line
128 A-Law and u-Law are specified in ITU Recommendation G.711.
132 device driver and this manpage were written by
133 .An Hellmuth Michaelis Aq hm@FreeBSD.org .