The Care and Feeding of ISDN4BSD
12 Setting up the	12 Setting up the	12.2 isdnd.rc Setup

12.1 Overview

The components involved in the answering system are the following:

The isdn daemon isdnd has to be configured to handle the connection establishment over the D-channel. Incoming calls as well as outgoing calls (see 3.2.8) are possible (The outgoing call mechanism is very preliminary and may change in the future - because of this it is not documented here) and it does not matter, if the originating side calls from an ISDN or an analog telephone. Once the connection to the remote site has been established, a B-channel is connected to the i4btel character device driver, and if configured to do so, it performs some audio format conversions and makes the audio data available at one of the /dev/i4btel<n> devices in userland.

What does each component do?

• [isdnd]the isdn daemon is configured by its configuration database isdnd.rc. It needs at least the own telephone number and a wildcard remote telephone number and some parameters for handling the timeout mechanism. Isdnd is just responsible for setting up and shutting down an ISDN connection from a remote telephone, once a connection is active, it connects a B-channel to a driver as specified in the isdnd.rc config file and thats it. It is not involved in any data transfer on the B-channel. For more information consult the isdnd(8) and isdnd.rc(5) manual pages.
• [i4btel]this is a character device driver which is visible (for example) as device /dev/i4btel0 in the userland. The optional audio conversion can be configured by use of the isdntelctl(8) program. For more information consult the i4btel(4) and the isdntelctl(8) manual pages.