Primary / Secondary Operation Basics - Futurecom DVRS User Manual

Primary / Secondary Operation Basics

The DVRS has a built-in simulcast prevention mechanism, which prevents more than
one DVRS to transmit on the same frequency, at the same time, in the same location.
NOTE:
The algorithm is intended to operate in stationary, same scene scenarios only. It cannot
be applied to moving vehicles. Moving vehicles must either have the DVRS switched
OFF or 'VR Disabled' MSU mode selected.
The DVRs are capable of communicating with each other and negotiating which DVR is
a Primary, i.e. elected to repeat, and which DVRs are on Secondary for as long as there
is a Primary.
The simulcast prevention algorithm has two phases:
•
Primary / Secondary Phase
•
Busy Lockout Phase
During the 'Primary / Secondary' phase, the DVRs exchange P25 messages on their Rx
frequency. When a DVR is activated (switched to System or Local mode), it sends a
query – "Is there a Primary?" If it receives a Primary (or Permanent Primary) 'Heart
Beat', then the DVR assumes Secondary state. If no Primary Heart Beat is received, the
DVR becomes the Primary and starts sending 'Primary Heart Beats' notifying other
DVRs of its status.
The 'Secondary' DVRs monitor any DVR-related activity while in a Standby mode and
execute Primary/Secondary checks periodically.
The 'Primary' DVR services any communication requests in the area and
'communicates' its status to the other DVRs periodically.
The Busy Lockout phase serves as an added protection by forcing the Primary DVR not
only to periodically communicate with the other DVRs in the area (using its Rx
frequency) but also to check for any activity on its Tx frequency prior to every repeat. In
order to accommodate the dynamically changing "real life" environment, i.e. DVRs
arriving or leaving the scene at random time, DVR channel / mode changes, Permanent
Primary activation, Remote DVR steering, etc., the Primary / Secondary algorithm has
several built-in layers, configurable in the DVR programmed personality.
The 'Permanent Primary Status Enable' field (in the Primary/Secondary Setup
Menu) is disabled by default and should be used only in special applications such as at
remote, fixed DVR installations, during testing or by selected public safety personnel.
The Primary / Secondary Status of a DVR is re-evaluated every time one of the following
takes place:
•
Change of DVR channel frequency
•
Change of DVR mode
•
Remote activation of another DVR
•
Selecting a DVR Disabled TG / Channel on the MSU
January 2019
8A083X30 Rev.11
APX Series P25 Interface
DVRS User's Guide
Page 39 of 94