MPT 1327 is a Private Mobile Radio (PMR) trunking protocol developed in the early 1980s by British telecommunications manufacturers, with assistance from the UK Department of Trade and Industry.

Conventional, non-trunked PMR services have only one channel, and can only be used by one person at a time. A trunking system allows a number of users to share a set of channels. If no channel is free at the time a user makes a call, the call will be placed on hold for a few seconds until any channel becomes available. Trunking results in higher quality of service and far fewer frustrated users.

MPT 1327 Operation
'Each radio station transmits a control signal on a radio channel. It also has a number of "traffic" channels at its disposal on which users of radio units communicate. When not in use, the radio unit is automatically tuned to the control signal and the unit's microprocessor can communicate with the system computer on this channel at any time.

When the user wishes to make a call, the unit transmits the request in the form of a data signal to the system computer. the computer finds the caller's desired correspondent and, by means of the control channel, checks for willingness to receive a call. When both called and calling parties are ready to communicate, the computer allocates the first available "traffic" channel.

When either party terminates the call, the radio unit sends a data signal releasing the channel.

Radio stations may be interconnected to increase the service area to provide any size of network, up to a national or international level.

Calls may also be made into other fixed line networks such as telephone systems.

MPT 1327 Benefits:
  • Quick Setup
  • Flexible, customizable standards
  • Common protocol allows international compatibility, and easy transfer of equipment from region to region and country to country.
  • Commonly defined standard allows equipment to be produced less expensively
  • User Features

    • Two-way conversation with a variety of types of call.
    • Data transmission: status messages (a number from 0 to 31) short data messages (alphanumeric characters) non-prescribed data (files, printing, etc...)
    • Call transfer
    • Automatic call holding until a channel becomes available.
    • Priority and urgent calls.
    • Ability to call: individual radio units a group of units all the units on the system
    • 'Call me back' facility when unit is unattended.
    • Allows the user to roam across boundaries.

    System Features

    • Protocol capacity - one million addresses per system code.
    • Traffic jam prevention controls.
    • Interference prevention.
    • Automatic user location and registration.
    • Automatic release of traffic channels at call termination.
    • Periodic checking of serial numbers for subscriber security.
    • Standards designed to support any size of system, from local to international networks.