Up to about 10 screens in one building, set each display's own scheduler and its power-on input. Above that, put one NTP-synced controller in charge and send on and off commands over the network. HDMI-CEC from a player suits one player feeding one screen.
There are four ways to put a building of screens on one clock, and the screen count picks the way. Up to about 10 screens, set each display's own on and off times and its power-on input; there is nothing new to buy. Past that, put one network-connected controller with an NTP-synced clock in charge and send the on and off commands over LAN. HDMI-CEC from a player works well too, but only where one player feeds one screen. This page compares the four routes by wiring, editing effort and what happens after a power cut, and ends with the choice for each case.
What each method switches
Each display's own scheduler. Commercial displays keep a clock and an on and off schedule in their setup menu, usually near the hospitality or store settings. Pair it with two more settings: power on when mains returns, and start on the input you want. That pair is what installers call hotel mode. It needs no network, no player and no controller, and it does not depend on anything else in the building.
The player's schedule, with the display set to follow. The media player turns its output on and off on its own daily schedule; the display sleeps when the signal disappears and wakes when power or signal returns. On a self-contained screen that plays its own files with no computer, such as our panel-mount range, the player is already inside. We show the daily schedule for one retail display in scheduling a display on and off daily, and the choice of one player or one per screen is covered in one signage player or one per screen for four TVs.
HDMI-CEC from the player. A player that speaks CEC sends power commands down the HDMI lead and the screen follows. CEC is a single bus per HDMI link, so one player reaches one screen. The enabling setting is covered in the HDMI-CEC setting that turns screens on. Where one player drives several displays, CEC reaches only the one on its own lead; the rest follow signal or their own schedules, as set out in one Android signage player driving multiple displays.
Commands from one controller. Commercial displays accept power on and off commands over RS-232 or LAN. The display's manual prints the command set, and the maker's management software sets power on and off from a PC. One controller holds the schedule, syncs its clock over NTP, and sends each command to each screen's address at the set times. Copy the serial command bytes from the manual; they differ between makers.
Side by side
| Method | What holds the times | Wiring per screen | One edit changes all | Pick it when |
|---|---|---|---|---|
| Display's own scheduler | Each display's clock | None beyond power | No | Up to about 10 screens, hours change rarely |
| Player schedule | The player's daily schedule | Player power and its video lead | No | Every screen already has its own player |
| HDMI-CEC | The player's schedule, sent as commands | The HDMI lead only | No | One player per screen, CEC-capable displays |
| Controller over LAN or RS-232 | One NTP-synced schedule | A network drop per screen | Yes | Above about 10 screens, or several floors |
| Switched power feed | A timer or contactor on the circuit | Mains work by an electrician | Yes, per circuit | Screens share one feed |
The fifth row is a variant of the first. Instead of each display scheduling itself, a timer or contactor cuts the whole circuit, and every display set to power on with mains comes up on its default input. It suits a corridor of screens on one feed. Mains switching is electrician work. Our screens run from a low-voltage DC feed, 12 to 36 V DC on the panel-mount series; the cabinet side is a rail-mount DC supply such as the DIN-rail supply in our accessories range, and the wiring is covered in our guide to wiring 12 to 36 V DC power.
How far each control signal reaches
RS-232 is a short run. TIA/EIA-232 allows the receiver to see 2,500 pF of load, and common serial cable adds roughly 50 pF per foot, so 2,500 pF ÷ 50 pF per foot = 50 ft, about 15 m. A controller's serial port serves the screens near it; everything farther travels over the network.
Ethernet is the long run. A structured-cabling channel reaches 100 m from the cabinet under ANSI/TIA-568, and most buildings already have a drop at or near each screen position, so LAN control usually adds no new cable.
CEC rides the HDMI lead between player and screen, so the lead length sets the layout. A passive HDMI lead is dependable to roughly 10 to 15 m at 1080p.
Where each method wins
- One floor, hours that change a few times a year: the display's own scheduler. Nothing to buy, nothing to network, nothing to configure beyond the screens themselves.
- A corridor of screens on one power feed: the switched feed. One timer does the whole bank, provided every display powers on with mains.
- Screens that each have their own player already: schedule the players and let the displays follow signal. No control layer to add.
- One player per screen on CEC-capable displays: CEC. The content schedule and the power schedule are the same document, and there is no extra hardware at the display.
- A building of screens, several floors, one IT cabinet: LAN control from one NTP-synced controller. Serial from that controller reaches only the screens near it, so the network is the carrier.
Worked example: 12 screens in a school
A two-story school hangs 12 screens: 10 in corridors and entrances, 2 in the office. Screens come on at 07:30 and go off at 16:30 on school days, which is 9 hours a day of lit time.
Route 1, per-display schedules. Setting one screen's schedule takes about 5 minutes including the walk, so installation takes 12 × 5 = 60 minutes. Each screen keeps its own clock, so the two clock changes a year call for 12 × 2 = 24 checks, and three term-time revisions a year call for 3 × 12 = 36 edits. Yearly editing effort: (24 + 36) × 5 minutes = 300 minutes, about 5 hours.
Route 4, one controller over LAN. The corridor positions already have network drops, and the 100 m channel from the cabinet covers every one, so wiring cost is zero. One schedule holds 07:30 and 16:30. Three term-time revisions are 3 edits at about 5 minutes each = 15 minutes a year, and NTP corrects the controller's clock at both changes, so the 24 clock checks disappear.
Route 3, CEC, would hang 12 players in the ceiling, each with its own schedule: the same 300 minutes a year of editing, plus 12 players and their power adapters to maintain. Route 2 leaves the 2 office screens without a player unless they get their own.
Decision: at 12 screens, LAN control does the same job with 15 minutes of yearly editing against 300, a twentieth of the effort, and no per-screen clocks to check.
Test one screen before you set the rest
- Cut the power for 10 seconds and restore it. The screen should come on to its default input without being touched.
- Send one off command and one on command by hand: from the controller over LAN, from the player for CEC, or at the timer for a switched feed. The screen should drop to standby and return within a few seconds each way.
- Set tomorrow's schedule and let it run. Check the on time, the off time and the input the screen wakes on.
- After the next clock change, check the screen came on at the right minute.
Four checks on one screen, one visit, then copy the settings to the rest.
The decision
Up to about 10 screens in one building and hours that change a few times a year: display schedulers, power-on set to the default input.
Every screen already fed by its own player: schedule the players and set the displays to follow signal.
One player per screen on CEC-capable displays: CEC, with the setting checked on every screen.
More than 10 screens, several floors, or screens that must be driven from one place: one controller or management application on the LAN, clock synced over NTP, command sets taken from each display's manual.
A bank of screens sharing one circuit: a switched feed and displays that power on with mains.
Recommendation: Count the screens before you buy anything. Take the per-display scheduler up to about 10 screens, and write the times on the wall box lid or a shared note so the next person can find them. At 11 or more, put one NTP-synced controller on the network, keep each display's manual command set beside it, and set every display to power on with mains on its default input, so after a power cut every screen comes back on its own to the right input and the schedule takes over.
Questions
Will a consumer TV work, or does this need commercial displays?
Both can switch on a clock. A commercial display carries a duty rating for how many hours a day the panel is lit, its manual prints LAN and RS-232 command sets, and its menu includes the power-on input setting. A consumer set has the scheduler and the input setting but rarely documents control commands, so central LAN control is out. Match the panel's duty rating to how many hours a day the screen will be on, and buy the commercial type wherever you plan to drive it from a controller.
What happens after a power cut?
A display set to power on with mains and start on its default input returns to service without a visit, and the schedule then takes over, whether that schedule lives in the display, in the player or in the controller. Test it on one screen first: switch the power off for 10 seconds, restore it, and check the screen comes back on the right input at the next scheduled time.
Can your screens join a central on/off schedule?
The panel-mount units are self-contained Android players: the daily on and off times are set on each unit, they take no video input, and we publish no duty-cycle rating for these units. Below about 10 units, set each unit's schedule and keep a written copy of the times. For larger banks, ask us about the current wall range, which is quoted per project.
Do on and off times survive the daylight saving changes?
A screen or player that keeps its own clock needs a check at each change; a controller synced over NTP does not, because the network corrects its clock. If the times live on the displays, budget one check per screen per change: 12 screens means 12 checks, twice a year. That per-screen clock is what pushes larger buildings to one controller.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.