Mototrbo transmit interrupt in conventional environments

Capacity Max systems have a granular system of call priorities which allow, for instance, a supervisor initiating a priority call to tear down calls of a lower priority where a free slot is not available.

Conventional (digital direct mode and single site repeater mode), IP Site Connect and Capacity Plus systems do not recognise priorities, but radios can still be programmed to interrupt others.

Transmit interrupt is a Mototrbo proprietary feature, not a DMR standard. Some third-party manufacturers have implemented similar features.

The ability to be interrupted and the right to interrupt others is set per-radio and per-channel or system. All radios may have the right to interrupt to make an emergency call, with managers’ radios additionally able to interrupt with group calls on their relevant department channel.

Types of interruption #

‘Transmit interrupt’ covers four different types of interruption in Mototrbo. Each type can be used independently or in combination with others and applies to group calls, private calls, emergency calls and all calls.

Remote voice dekey
End an ongoing call. Used to clear the channel when a PTT has been held inadvertently.

Voice interrupt
End an ongoing call to start your own. Used to broadcast urgent information during an long call.

Emergency voice interrupt
End an ongoing call to start an emergency call. Used to prioritise air time to emergency calls.

Data over voice interrupt
End an ongoing call to transmit data. This isn’t used by any built-in application but is available to third-party applications on an option board or attached computer. Used when data is more important than voice.

Interrupted radio configuration #

The radios to be interrupted need to be configured to allow interruption, else it will be ignored. This is set on a per-channel basis and applies to all three types of interruption.

Allow Interruption: Enable
TX Interruptible Frequencies: Enabled for simplex*
*TX Interruptible Frequencies is only required for simplex channels and indicates that the interruption will come from another radio, rather than a repeater.

Interrupting radio configuration #

Remote voice dekey
Assign a button with the personality ‘TX Interrupt Remote Dekey’.

Voice interrupt
Set In Call Criteria to ‘TX Interrupt’ for a given channel.

Emergency voice interrupt
Enable TX Interrupt for a given emergency system.

For obvious reasons, Motorola recommend limiting remote voice dekey and voice interrupt to trained and trusted users. Emergency voice interrupt, on the other hand, merely assists the good functioning of an emergency system.

Notes #

Interrupts typically take no longer than two seconds in direct mode or three seconds in single site repeater mode. If unsuccessful, the radio will automatically retry interrupting once, doubling this time.

VOX cannot be used with transmit interrupt and will be disabled.

More information is available from Wayne Holmes’ blog and wiki.