What feature allows EF Johnson radios to monitor one channel while checking others?

The scan feature is specifically designed to allow users of EF Johnson radios to continuously monitor one active channel while simultaneously checking for activity on other channels. This capability ensures that important communications are not missed, as it enables the radio to quickly switch between channels based on the presence of signals.

The effectiveness of the scan feature lies in its ability to provide situational awareness by keeping the user informed of transmissions that may occur on other channels without requiring the user to manually switch back and forth between channels. This is particularly useful in scenarios where real-time communication and responsiveness are critical, as users can react promptly to any important messages or alerts from any of the monitored channels.

In contrast, the other options do not encapsulate this functionality accurately. For instance, auto-scan refers to programmed scanning that automatically shifts between channels based on specified criteria, while manual scan would require the user to actively switch themselves. Dual channel typically indicates the capacity to operate on two channels at once but does not specifically focus on the scanning aspect involved in monitoring multiple channels for activity.