Prevent users from talking over one another with this one setting.

Q We have a situation where if multiple people key up at the same time, often more than one of them connect successfully and end up overtalking each other, resulting in a garbled transmission. Are there any settings that can help prevent this?

A Yes, there are two settings you are looking for: Enhanced Channel Access and TX Admit Criteria.

Enhanced Channel Access is a channel access procedure that utilizes a high-speed handshake between a calling radio and a repeater, which takes approximately 120 milliseconds to complete.

When a user initiates a call, the radio first transmits a channel access request and listens to the channel to determine the status of that request. The radio will only proceed with transmitting the actual call once channel access has been obtained. In effect, Enhanced Channel Access reserves the channel for the initiating radio and grants it exclusive access for a short duration, ensuring that only one requesting radio obtains the channel at a time.

Remember that this is a digital-mode feature. There is nothing quite like this in analogue-mode.

Enhanced Channel Access also only works when the radio's TX Admit Criteria is set to Channel Free or Color Code Free. Setting TX Admit Criteria to Always bypasses Enhanced Channel Access.

If you are going to set TX Admit Criteria to Channel Free, make sure you read this.

If enabled, Enhanced Channel Access is also used for Data and Control (CSBK) calls.

Enhanced Channel Access greatly improves the success rate of voice and data calls by minimizing over the air collisions that occur when multiple radios attempt to key up at exactly the same time. It also prevents a radio from transmitting blindly if it is out of the inbound (receive) range of the repeater, providing the user with a out of range indication of sorts.

The trade-off is that the handshake (TRART) process slightly increases the system access time for voice calls and adds latency to data and control calls (e.g. Radio Check; Radio Disable).

On a single site and IP Site Connect system, Enhanced Channel Access can be enabled as described above. However, on a Capacity Plus (Single Site and Multisite) system, this feature is built into the call start up process for Trunked Channels, and does not need to be (cannot be) configured by the user. However, it can be manually enabled on Capacity Plus Data Revert Channels.

With Capacity Max, Enhanced Channel Access is used to manage floor control for transmissions within a call.

Enhanced Channel Access is also supported on a repeater operating in Extended Range Direct Mode (single frequency repeater) but only when Compatibility Mode is disabled.

Enhanced Channel Access is however not supported on MOTOTRBO Link (repeater backhaul) systems. Repeaters also do not support Enhanced Channel Access on Dynamic Mixed Mode channels or Enhanced GPS (scheduled) Revert channels - the latter has its own means of avoiding data collisions.

.