Project 25 digital radio systems optionally support a trunking mode of operation. This document provides an overview of the essential attributes of the trunking control channel messaging such that, where systems are configured in the trunking mode, voice and data services operate in accordance with the goals of Project 25:

• support any Project 25 trunking radio,

• interoperate across any Project 25 digital radio trunking system,

• independent of the particular equipment manufacturer,

This document describes the presentation on the trunking system with respect to the Inbound Signaling Packet (ISP) and Outbound Signaling Packet (OSP) of the control channel.