This device is view-only: it follows the host live and rings every bell. Enter the host PIN to control the timer from here.
Start, pause, and reset from here reach every open device within about a second. More than one device can be unlocked at a time; the latest action wins.
Every device computes the countdown from the shared start time (corrected against the server clock) and rings its own bells locally, so alarms stay simultaneous even on a slow connection. Enable sound once per device and keep screens on and unmuted.