The type of the endpoint that triggered the register or
unregister event.
none - No endpoint is associated with this event.
other - An endpoint type other than the ones listed below.
gatekeeper - The endpoint is a Gatekeeper.
gateway - The endpoint is a Gateway (and not a proxy).
mcu - The endpoint is a Multipoint Control Unit.
terminal - The endpoint is an H.323 terminal.
proxy - The endpoint is a Proxy.