# Defining the switch fabric

A switch fabric definition begins with a Fabric statement and ends with an End Fabric statement. All statements appearing between these two keywords define the switch fabric for the system.

A switch fabric definition has four basic components:

Component | Description
General attribute section | General default attributes for the switching fabric.
Bus definition section | Telephony buses in the system.
Switch configuration | Configuration of each board in the system.
Switch connections | Connections in the PPX configuration file made during PPX initialization.

The format of the PPX configuration file is:

[PPX]
Fabric
# fabric attribute(s)
# bus definition(s)
# switch definitions
# switch connections
End Fabric

All configuration information for the system must exist inside the Fabric statement.

The following illustration provides an overview of the PPX configuration file and its structure. The example system contains two boards. The PPX configuration file has a bus definition section describing the bus connecting the boards. Each board also has a switch configuration section.

## Switch fabric attributes

Specify the default silence pattern used by the PPX server with the switch fabric attribute:

IdleCode = [MU_LAW | A_LAW]

This attribute must appear immediately following the configuration file keyword Fabric, but before any of the other configuration data, as the following example shows:

[PPX]
Fabric
IdleCode = MU_LAW
# bus definition(s)
# switch definitions
# switch connections
End Fabric

If this attribute is not present within the file, the default value used is MU_LAW (0x7F).

The value of the IdleCode attribute is used as the default idle pattern for connections created with a NULL passed as the parameter pointer.