How to use the online alarm clock
Before the relief crew is due on the railway tracks, use 3:42 am as the point for checking names, access arrangements and protective equipment. Setting the alarm in advance leaves 18 minutes for those final preparations before 4:00 am, without making the round hour itself the first prompt to move.
With staff waiting for clearance, confirm where the alarm sound will actually play. Headphones can remain connected unnoticed, sending the alert away from the room and making a visible volume setting misleading. Test the tone briefly, then leave the headphones disconnected if the sound needs to reach everyone nearby. If the browser alarm stops running beforehand, the crew will receive no alert, so keep a separate railway procedure or staffed check for anything safety-critical.
For a planned release during the night, have a small drink and any light food before the final checks begin, keeping both away from paperwork and equipment. A heavy meal is easier to leave until after the crew has gone out and the immediate activity has settled. At 3:42 am, a covered bottle placed somewhere deliberate is less distracting than hunting for a drink during the remaining preparations.
Common questions
Can I change the sound?
Yes, there is a short list of tones to pick from before you press Start. Softer sounds are easy to sleep through, so a firmer bell tends to be the safer choice for anything early in the morning.
Will it still be right when the clocks change?
Yes. It reads your device's local clock, so the move between GMT and BST at the end of March and October is picked up automatically, as long as the computer's date, time and time zone are set correctly.
Can I use this on a phone?
It works in a mobile browser, but phones lock the screen and suspend background tabs far more readily than a laptop does, which can stop the alarm sounding. For anything important, a desktop or a plugged-in laptop is the steadier option.
Does the alarm still work if I close the tab?
No. Everything runs inside this page, so closing the tab — or quitting the browser altogether — ends the countdown there and then. Leaving it open in the background is all it asks, and switching to another tab makes no difference.