Transmit Interrupt
The Transmit Interrupt feature is a suite of features proprietary to Motorola Solutions.
This feature generally allows a radio to shut down an ongoing interruptible voice transmission, and potentially initiate a new transmission. Transmit Interrupt is independent of call type, therefore it applies to Group Calls, Private Calls, Emergency Calls and All Calls. This feature also applies to remote monitor responses[1].
Configuration Options
To support different use cases, Transmit Interrupt has four unique variations:
Voice Interrupt This feature allows a radio that is unmuted to an interruptible voice call, to stop the ongoing voice transmission and initiate its own voice transmission to the same call membership. Voice Interrupt is typically used during a prolonged voice transmission when “late-breaking” or urgent information becomes available, and it is necessary to disseminate the information to the group as quickly as possible.
Emergency Voice Interrupt This feature allows a radio to stop any ongoing interruptible voice transmission, and initiate its own emergency transmission. Emergency Voice Interrupt gives a radio an improved access to the radio channel, in an emergency condition.
Remote Voice Dekey This feature allows a radio to stop an ongoing interruptible voice transmission. It is typically used by a supervisor to remotely dekey a radio that is inadvertently transmitting (for example, the PTT is inadvertently pressed for an extended period of time) and occupying the radio channel.
Data Over Voice Interrupt This feature allows a third-party data application on an option board or attached PC to control the radio in order to stop any ongoing interruptible voice transmission and initiate its own data message transmission. The application can also specify in the data message, an option to discard itself, if an ongoing voice transmission is not interruptible. This feature is useful in situations where data traffic is more important than voice traffic. Data Over Voice Interrupt is not used by any data applications native to the radio (for example, Text Message, Location, and Telemetry do not use Data Over Voice Interrupt).
The above would be set up in the CPS or Radio Management.
Simplex and Single Site
While receiving a Direct Mode or Dual Capacity Direct Mode transmission, a radio may use the Transmit Interrupt feature to remotely dekey the transmitting radio and begin its own Direct Mode or Repeater Mode transmission. Similarly, while receiving a Repeater Mode transmission, a radio may use the Transmit Interrupt feature to remotely dekey the transmitting radio, and begin its own Repeater Mode transmission. However, the radio may not use the Transmit Interrupt feature to remotely dekey the transmitting radio’s Repeater Mode transmission and begin its own Direct Mode transmission. This scenario is not supported because Transmit Interrupt dekeys only the radio’s transmission within a channel (timeslot), but does not dekey the repeater which remains keyed on the Direct Mode carrier frequency, and supports two channels (timeslots). The repeater is not dekeyed because this may interfere undesirably with a call in the other channel (timeslot) supported by that repeater.
Provisioning of the Transmit Interrupt feature in general, is separated into two basic categories:
- Radios that have the ability for voice transmissions to be interrupted.
- Radios that have the ability to initiate transmit interrupt commands.
The radios may be provisioned with none, one, or both of these capabilities.
There are a few important items to consider before provisioning of the Transmit Interrupt feature:
- The Transmit Interrupt feature is supported in digital direct mode and single site repeater mode.
- Because the Transmit Interrupt features are proprietary to Motorola Solutions and use some proprietary signaling (that is, manufacturer-specific extensions that comply to the ETSI DMR Tier 2 standards), non-Motorola Solutions radios may not be able to unmute to an interruptible voice transmission and Motorola Solutions radios may not be able to interrupt a non-Motorola Solutions radio’s voice transmission. Hence, it is highly recommended to assign radios to separate groups and/or channels. This classifies radios provisioned with Transmit Interrupt capability from the radios that are not provisioned with the capability.
- In Direct Mode, Transmit Interrupt can typically clear an interruptible voice transmission from the channel in less than two seconds. In Single Site Repeater Mode, Transmit Interrupt can typically clear an interruptible voice transmission from the channel in less than three seconds. The Transmit Interrupt feature provides one automatic retry in the event that the first interrupt attempt fails due to corrupt signaling (for example, RF coverage degradation, signaling collisions with other radios, and others). The retry essentially doubles the times mentioned. If the radio user still needs to interrupt after the failed retry, the user needs to initiate another service request.
- VOX is not compatible with the Transmit Interrupt feature. Therefore, VOX is prevented from operating when any of the Transmit Interrupt features are enabled.
Limitations in older firmware versions
Transmit Interrupt was introduced in software release R01.06.00 (otherwise known as R1.6) Initially, this feature was only supported on digital direct channels and digital repeater channels. As of R01.07.00, this feature is supported on IP Site Connect wide area channels as well as on Capacity Plus systems.
There are several considerations when upgrading a deployed system that presently do not support the Transmit Interrupt feature, to become Transmit Interrupt capable.
For systems that use a DR 3000 repeater, the repeater software version must be upgraded to R01.07.00, or later. For systems that do not use privacy exclusively, radio transmissions with privacy disabled and interruptible voice enabled cannot be received by radios using software versions prior to R01.06.00.
For systems that use privacy exclusively, there are no major concerns receiving radio transmissions with both privacy and interruptible voice enabled; provided the older release supports the type of privacy being used by the radio provisioned with software version R01.06.00 or later.
To minimize service disruption during the upgrade period, systems that do not use privacy exclusively may be upgraded using the following approach:
- Provision new radios with software version R01.06.00 or later. Configure two channels; one channel with Transmit Interrupt features enabled, and the other channel with all Transmit Interrupt features disabled. During the upgrade, the channel with all Transmit Interrupt features disabled is used.
- Individually upgrade previously deployed radios to software version R01.06.00 or later, and provision with the two channels described above. The channel with all Transmit Interrupt features disabled is then used during the upgrade.
- For systems that use a repeater, the repeater may be upgraded to be Transmit Interrupt capable at any time. Finally, once all radios have been upgraded to the compatible software version, the channel with the Transmit Interrupt features enabled is used by all radios on the system.
IP Site Connect
For IP Site Connect wide area channels, a repeater can use this feature to stop a voice transmission where a radio continues to transmit even after failure of arbitration.
The Transmit Interrupt feature is supported on both local and wide area slots of an IP Site Connect system.
Capacity Plus
The Transmit Interrupt feature is supported on both local and wide area slots of the Capacity Plus Single Site and Capacity Plus Multi Site system configurations.
Capacity Max
Transmit Interrupt is supported in Capacity max but the purpose and function is slightly different.