This object specifies the voice mode for IP IP connections.
normal : A normal Mode is a transcoding mode for IP-IP
connections where the bearer properties will
be different on two ends of a call.
fastRoute : A voice call will be esatblished in this mode
when the codec is same on two ends of a call
but packetization period is different.
tranparent : A voice call will be established in transparent
mode when the all the bearer properties for a
voice call are same on the two ends of a call.