# Asterisk Project : Channel Driver Modules

Added by malcolmd , edited by mdavenport on Sep 23, 2010

All calls from the outside come through a channel driver before reaching the core, and all outbound calls go through a channel driver on their way to the external device.

The SIP channel driver, for example, communicates with external devices using the SIP protocol. It translates the SIP signaling into the core. This means that the core of Asterisk is signaling agnostic. Therefore, Asterisk isn't just a SIP PBX, it's a multi-protocol PBX.

For more information on the various channel drivers, see Section 400. Channel Drivers and External Connectivity.

All channel drivers have a file name that look like chan_xxxxx.so, such as chan_sip.so or chan_dahdi.so.