A little bit on the MPT1327 System ID



I got asked about MPT1327 the other day and thought I should share the same information with the Motorola community. 

One channel in a MPT1327 trunked system is allocated to operate as a Control Channel. The Control Channel continuously transmits information about calls and the system itself. Radios which are not in a call will monitor the Control Channel – these radios will also remain muted

Calls are set up using the Control Channel and when a radio is called, it will move from the Control Channel to one of the Traffic Channels allocated by the system.

The information sent out on the Control Channel is known as the Control  Channel System Codeword. This Codeword is made up of 128 bits and is sent continuously on the control channel at 1200bps using FFSK. 64 bits of this Codeword contain address information (which calls are active) and the other 64 bits contain system information (known as the System Codeword). Within the latter 64 bits, is the System Identity.

The System Identity is contained within the System Codeword and occupies 15 bits. The System Identity contains the following information:

System Type: Regional or National.

  • Operator Identity: 2 or 7 bits. The customer or telecommunications regulator will allocate this number  and it depends on whether the system is a regional or national network.
  • Network Dependent Data: There are three parameters included within NDD, these include Area Zone and SIL. These allow the customer to segregate the system into areas which users can or cannot operate in. The number of bits allocated to this is dependant on whether the system is regional or national.
  • Label: Each site can have a label that can be used to prevent radios from registering on that site.

The below diagrams shows two examples of a MPT1327 System ID. The first one is a regional network hence bit 1 is set to zero. In both cases the Operator ID is 1 (decimal).

Also, in both cases the NDD is set to nothing so the system ID does not provide a means for restricting users from specific sites. The Label subfield is set to 001 which equates to Category A in the CPS and system management software.

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Type
Operator ID
NDD
Label
0
0
0
0
0
0
0
1
0
0
0
0
0
0
1
In the above example, the system ID is represented as 0081 in Hexadecimal.

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15
Type
Op. ID
NDD
Label
1
0
1
0
0
0
0
0
0
0
0
0
0
0
1
In the above example, the system ID is represented as 5001 in Hexadecimal.

The System ID, to which the radio is registered or has scanned, can also be seen by pressing 120#6 on a portable radio keypad.

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