Forty-nine minutes is seven sevens, a full circuit of equal stations. Seven minutes is short, so each station needs a card with the steps.
Test one station yourself before the room starts. A confusing card costs every group the same seven minutes. Press space to start or pause, R to reset, and F for fullscreen. The screen can stay awake after you start, using the wake lock your browser allows. Pick the alarm before you begin. A bell, a chime, a beep, or a short digital pulse all come from the Web Audio API, so there is no sound file to wait on.
This page is the 49 minutes countdown and nothing else is running underneath it. Related lengths are linked under the guide if you want a neighbor, and the timer itself stays above the fold.
Questions
How do I run a 49 minutes timer on a projector?
Press start, then F or the fullscreen button. Classroom mode hides the writing so the digits fill the wall. Test one station yourself before the room starts. A confusing card costs every group the same seven minutes.
What is 49 minutes actually good for?
Forty-nine minutes is seven sevens, a full circuit of equal stations.
Will the countdown drift if I switch tabs?
No. The end is a timestamp. The display is the gap between that timestamp and now, so a background tab does not lose seconds the way a ticking counter would.