30 System Feature Overview
While receiving a Direct Mode/Dual Capacity Direct Mode (DCDM) 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:
1. Radios that have the ability for voice transmissions to be interrupted.
2. Radios that have the ability to initiate transmit interrupt commands.
NOTE: 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, single site repeater
mode, on both local and wide area slots of the IP Site Connect mode, Capacity Plus,
and on Linked Capacity Plus system configurations.
• In Capacity Plus and Linked Capacity Plus configurations, an All Call can only be
stopped by Emergency Voice Interrupt. Voice Interrupt, Remote Voice Dekey, or Data
Over Voice Interrupt features are not supported.
• Because the Transmit Interrupt features are proprietary to Motorola and use some
proprietary signaling (i.e., manufacturer-specific extensions that comply to the ETSI
DMR Tier 2 standards), non-Motorola radios may not be able to unmute to an
interruptible voice transmission and Motorola radios may not be able to interrupt a non-
Motorola 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 (e.g., RF coverage
degradation, signaling collisions with other radios, etc.). The retry essentially doubles
the times shown above. 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.
NOTE: For the Transmit Interrupt feature to operate consistently, all radios using the channel
should be provisioned with the ability to be interrupted. If some radios are provisioned
without the ability to be interrupted (e.g. normally desirable for a supervisor’s radio), then
those radios’ transmissions cannot be interrupted.
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