As we all (obviously) know, VOIP protocols, such as IAX2, may be used for
transport of audio/signalling for uses other then phone calls, such as radio, in this case.
Therefore, an endpoint that accepts a VOIP connection processes/utilizes different
methodologies for a radio connection and a "traditional telephony" (like a phone call)
type of connection.
The "X" is used for a radio-style connection, and indicates to app_rpt that it is not to authenticate
the call (that is, authentication was done in the dialplan previous to "sending" it to app_rpt). This is
necessary for scenarios such as use with IAXRPT, where user authentication is done via means external
to app_rpt.
The "P" is used to make app_rpt accept a "traditional" telephony-style (VOIP SIP, IAX2, etc, or other telephony
interface, such as DAHDI) connection, and allow access to a node via a "telephone" call.
These are 2 very different operating environments.
Jim