The Care and Feeding of ISDN4BSD
12.1 Overview	12 Setting up the	12.3 Program Parameters

12.2 isdnd.rc Setup

The isdnd.rc entry for a telephone answering machine is simple:

#---------------------------------------

#    test - example of a configuration file for the i4b isdn daemon

#    last edit-date: [Fri Oct 30 16:27:45 1998]

#---------------------------------------

system

ratesfile               = /etc/isdn/isdnd.rates

useacctfile             = on

acctfile                = /var/log/isdnd.acct

acctall                 = on

#==============================================================================

# telephony test

#==============================================================================

entry                           

name                    = I4BTEL        # name for reference

usrdevicename           = tel           # ipr, tel, rbch

usrdeviceunit           = 0             # unit number

isdncontroller          = 0             # controller to use or -1 to use any

isdnchannel             = -1            # channel (1/2) to use or 0 or -1 for any

                                        # numbers used to verify at DIAL IN

local-phone-incoming    = 37            # we take calls for this local number

remote-phone-incoming   = *             # we take calls from this remote machine

dialin-reaction         = answer        # accept, reject, ignore, answer

answerprog              = answer        # program to use

b1protocol              = raw           # hdlc, raw

idletime-incoming       = 10

The system section should be obvious (if not, have a look the the sections describing the PPP and the IP over raw HDLC interface setups) and the entry section too - with some exceptions:

1. the keyword remote-phone-incoming now has a wildcard (``*'') parameter which allows anybody to access the answering machine,
2. the dialin-reaction is answer to select the telephony answering system
3. the b1protocol must be set to raw
4. and finally by use of the keyword answerprog a program or script under the directory /etc/isdn must be specified, in this case /etc/isdn/answer will run when someone calls extension 37.

Now what will happen when someone calls in ?

When a telephony call is coming in, the kernel will switch the B-channel trough to the selected /dev/i4btel0 device and isdnd will run the script selected by the answerprog keyword in background. Typically these scripts will copy some audio data to or from the /dev/i4btel0 by using the dd program.