State of Colorado

Digital Trunked Radio System

VHF - 800 MHz. Interoperability

 One of the key issues with the migration from the existing VHF (150 MHz.) conventional radio system to the 800 MHz. digital trunked radio system (DTRS) is inter-operability between the two systems.  There are two scenarios that require this type of inter-operability.  The first is for users who choose not to,  or cannot afford to migrate when the state does.  The second is for users who reside in an area that is not yet converted to the DTRS and travel into an area that has been converted. These requirements exist for communications between various state agencies and/or  with local and federal agencies

 In the design of the DTRS both of these scenarios have been considered and two methods will be available to establish inter-system inter-operability. The primary method will be to use inter-system access channels. The secondary method is to use the National Law Enforcement Emergency Channel (NLEEC)

 PRIMARY METHOD

 This method will be implemented to meet the requirements for users who reside in an area that has not migrated to the DTRS and travels into an area that has already migrated, and for direct unit to unit communications between users on the DTRS and those using existing VHF systems. 

A new VHF channel will be installed at the state tower locations when the DTRS is installed.  This  access channel will be the same within geographic regions.  Different regions will have different access channels in order to prevent interference.  These new VHF  access channels will be permanently cross patched to a specific channel (talkgroup) in the DTRS. VHF system users will need to have the access channel(s) programmed into their radios.  All  radios on the DTRS will have the access channels.  Users on both systems should scan the common channels for optimum usability.

 When a VHF users needs to communicate with a DTRS user, They will select the DTRS access channel and call the unit they wish to communicate with, whose scanner will hear the calling unit.  The called unit will then select the access channel allowing direct communications.  This method will also work in the other direction when a DTRS user needs to talk to a VHF user.  Multiple access channels will be installed in areas where one channel is not sufficient for high volumes of radio traffic. 

SECONDARY METHOD 

The use of NLEEC for mutual-aid communications between public safety agencies is the current method used for inter-agency communications.  All State Patrol communications centers are equipped with NLEEC as are many local government communications centers.  Every radio operated by state agencies is also equipped with NLEEC, as are the vast majority of local government radios.  NLEEC will remain in place in all State Patrol communications centers including the 5 new regional centers as they become operational.  NLEEC will allow direct communications with all State Patrol communications centers for those agencies who have not migrated to the DTRS.  A dispatcher will be able to “patch” NLEEC to a specific channel (talkgroup) on the DTRS for direct unit to unit communications when necessary.  The patch will not be the best method for unit to unit communications, since it requires dispatcher set up and knock down and may tie up NLEEC for extended periods..  NLEEC will be the primary channel for communications with State Patrol communications centers.  In areas where there are existing UHF (450 MHz.) users and the Colorado Law Enforcement Emergency Channel (CLEER) is used, it will remain and operate the same as NLEEC.

 The need for inter-system inter-operability was defined very early in the planning for the DTRS.  It is a high priority in the technical system design and will be an integral part of the system implementation.  With 2 methods available to achieve inter-operability, local and federal users will continue to be able to communicate with state agencies and with each other.