You may be hearing the term SIP a fair bit these days but what is it actually all about.
From a technical perspective Session Initiation Protocol (SIP) is an application layer control protocol that is commonly used in the VoIP telephone world for creating, modifying, and terminating sessions with one or more users. SIP can be used to create two-party, multi party or multicast sessions and is based on an RFC standard from the Internet Engineering Taskforce. Other protocols have been used in the past however SIP is now considered the number one protocol due to its simplicity, flexibility and ease of use.
To put this more simply lets take the example of a Police Station in a country town. Using the SIP capabilities built into the Omnitronics IPR110 Plus an operator can pick up a PBX phone in the office or at home and speak with remote radio users. These users could be at several locations throughout the region and on different repeater sites. Each call can be made to a specific repeater site. This provides an efficient use of the radio network. Calls can be set-up to talk to several repeater sites allowing greater connectivity over a wide area. After the conversation has finished, the call can be broken down leaving the network free for other users. There is no need for a centralized operator to monitor and control all calls as demonstrated in the diagram.
Call 1: An operator enquiry can easily be resolved with a temporary connection between the PBX extension and the northern region radio network.
Call 2: Police officers in one region can temporarily confer with other officers in other regions. Network wide calls can easily be made informing all personnel of a pending problem even though the radio networks are not normally connected.
Call 3: Police officers in the southern region can speak directly with the operator to seek clarification on an incident.