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Help — the end sound, time differences between screens, and screen roles

Three frequent questions in one place: "there is no sound", "phones differ by a few seconds", and "how do I split speaker and audience screens". Each section stands on its own.

The end sound — which device rings, and when to turn it off

The end sound is not a room setting but a setting on each device. A browser cannot play sound until the user has tapped something, so a participant screen opens with sound off, and only devices where someone taps the sound button will ring. When you turn it on, one short note plays quietly so you know it worked. The host cannot enable sound on participants' devices. At zero, each device with sound on rings once. It does not repeat.

The rules by situation are simple.

• Video calls and online classes: off. An end sound from a device with a live microphone goes into the whole call. Let people watch the end display; only the host turns it on.
• Classrooms, lecture halls, gyms: one device. Enable it on the screen connected to the speakers. Thirty devices ringing a few seconds apart is distracting.
• Exams: if the end is announced over the PA, leave it off; if the end sound is the signal, enable it on one front screen per room and check the volume with the preview.
• Alone: on.

If there is no sound, check in this order. Is the button showing "sound on" (people often tap it again and turn it off) → device volume and the iPhone side silent switch → was the screen off (a locked screen pauses the browser, and if zero passed while it was locked the sound will not play afterwards) → is another app using audio, such as a call → are Bluetooth earphones connected. That resolves almost everything; if not, try another browser.

If sound comes from everywhere, several devices have it on. Each reaches zero within about a second of the others, so the sounds scatter. In one space, keep it on one device and tap the button once on the others to turn it off.

The end is visible without sound. At zero the digits turn red, "Finished" appears large, and the overtime climbs like +00:15. Nothing flashes. Sound is for when nobody is looking at the screen.

Why screens differ by a few seconds

Two phones on the same link showing 00:30 and 00:28 is not a fault. The server does not send "29 seconds now" every second; it sends "this timer started at time X and is 5 minutes long" once, and each device counts on its own. That is why the digits keep going through a brief disconnection, and also why small differences can appear.

There are three causes.

• Device clocks differ. The timer uses the offset from server time measured at connection rather than the device clock, so a clock that is five minutes off still shows the right remaining time. If the network is slow at that moment, an error of around a second can remain.
• The screen was in the background. Phones slow or pause the browser when the screen is off or another app is in front. When it comes back, the timer re-syncs at once; for the few seconds before that, a stale number can show. Most "my screen is 3 seconds behind" reports are this, and they recover within seconds.
• Delivery time of the start. A device on a slow connection receives the start later, but it subtracts the time already elapsed as soon as it arrives, so it starts showing later rather than starting late. The number is right.

This is enough for anything people watch and act on: classes, meetings, events, exam announcements, workouts. It is not for frame-accurate or beat-accurate sync, and a legally significant time (exam end, deadline) should be confirmed by a person alongside the screen.

To reduce the difference: keep screens awake (lengthen the device auto-lock), open the link a minute before the start, prefer mobile data over crowded public Wi-Fi, and refresh once if it still differs. A refresh shows the running state again; it does not restart the timer.

Splitting moderator, speaker and audience screens

A room has only two links. The host link has start, stop, time changes and messages; the participant link has the digits and a sound button. Screen layout is decided by who opens which link where. The participant link shows the same thing on any number of screens, up to 500.

• Speakers need the digits where their eyes barely move: a lectern tablet (double-tap for fullscreen), their own phone (lengthen auto-lock), or a downstage monitor. Avoid layouts where the speaker has to turn round to the audience's big screen.
• Whether the audience sees it depends on the event. Competitions, class presentations, debates and exams call for fairness, so put the participant link fullscreen on the projector or a separate TV. For lectures, sales pitches, interviews and filming, keep it to the speaker and the crew.
• The moderator keeps the host link on a phone and operates while watching the talk. Two people, such as the moderator and a technician, can share the host link. Send speakers the participant link only. If a speaker received the host link, send the participant link again; if it has spread, create a new room.
• To put the same digits into a broadcast, follow the OBS overlay guide. Control still lives on the moderator's phone.
• Turn off the screen saver and sleep on the computer driving the audience TV; the browser's wake request cannot override device power settings. Bright halls and dark venues follow the system theme automatically; to pin one, add ?theme=dark or ?theme=light to the address.

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