ARA-1 Operations Manual
INTEROPERABILITY NOW
1-7
1.8
COR & PTT Signaling in the SIP Environment
Most radio systems are either simplex or half duplex, the important aspect to remember for both
types is that only one person can be heard at a time. With full duplex systems, all parties to a
conversation may be heard simultaneously: a telephone system is a good example. Most JPS
interoperability equipment can accommodate both types of systems, but
both
parties of a
conversation must be using full duplex equipment for either party to be able to simultaneously
talk and listen.
The same is true of interoperable communications using SIP; many SIP devices are capable of
Full Duplex operation (as are most phone-related voice communications devices). However,
when patched to a half-duplex radio, the conversation is limited to Half Duplex.
COR
: A signal that tells when a radio (or other communications device) is
receiving a valid signal (an output from the device).
PTT:
A signal that tells a radio (or other communications device) that a valid
signal is being sent to be transmitted (an input to the device).
Full Duplex:
System users can simultaneously talk to and listen to other parties
of the communications system.
Simplex or Half Duplex:
Only one system user can be heard at a time.
This section will help explain how these concepts affect the set up configuration options. More
details on the options in Section 2.
1.8.1
COR Handling in the SIP Environment
There are three basic components:
•
How the ARA-1’s radio interface determines that its associated radio is unsquelched-
how the “Active COR” condition is determined. Also called “Deriving COR.”
•
How this signal is sent over the network by the SIP Protocol
•
How the SIP device on the “other side” of the network knows that valid audio is being
sent to it.