Online alarm clock for 3:46 am
As you hand the urgent volunteer fire brigade call to the person taking over, set the alarm for 3:46 am so the changeover does not drift into guesswork. Confirm who now has the details and what remains outstanding before 4:00 am. That leaves a clear marker for your final responsibility rather than relying on a tired glance at the clock.
Before stepping away from the call, check whether your phone is on silent and raise the alarm volume if needed. Use the preview sound, then leave the browser page active with the phone awake and connected to power. If either condition ends, this browser alarm cannot sound, which could leave the brigade call handover without its planned warning. A separate physical alarm is sensible when missing the signal would disrupt the response.
Because this changeover happens deep in the night, keep the sound close enough for you to hear without carrying through the whole house. Place the phone on a stable surface beside you, lower unrelated notification sounds, and choose a brief tone rather than repeated ringing. If someone else is sleeping nearby, tell them why a 3:46 am alarm may sound and silence it promptly once the handover is complete.