These three devices sit within half a metre of each other at the guest room entrance, and together they handle the first and last impression of the room. They are also the easiest devices in the room to wire, which is why they are often given the least attention on the drawing.
All three connect to the RCU host by dry contact — no addressing, no configuration, no bus. The wiring is physical and one-to-one. This article covers how each connects and what to specify beyond the connection itself.
The Door Plate
The door plate is the outward-facing device: doorbell button, Do Not Disturb indicator, Make Up Room indicator, and a service status backlight visible from the corridor.
Wiring
The back of the door plate carries labelled signal terminals. Each label corresponds to a function — Do Not Disturb, Make Up Room, doorbell, common. On the RCU host, matching dry contact terminals are labelled the same way.
Wiring is a one-to-one match: each labelled signal on the plate lands on its counterpart on the host.
There is no address to set and nothing to configure at the device. If a function does not work, the fault is a wire on the wrong terminal or a loose termination — the diagnosis is quick, which is why door plates almost never cause commissioning delays.
Installation height
Reserve an 86 mm back box beside the door frame at 1.35 m from finished floor level.
This puts the doorbell button within comfortable reach for most adult guests and aligns visually with switch heights elsewhere. Below 1.25 m, shorter guests find it awkward to press cleanly. Above 1.45 m, the indicator display sits above the natural eye line when standing close to the door.
A common error on drawings is marking the door plate at 1.5 m or higher, usually because the height was copied from a room number signage detail rather than a control device detail.
The Doorbell
The doorbell has four conductors. Each is colour-coded, and on the RCU host there are four matching doorbell signal terminals.
Match by colour, terminal to terminal. As with the door plate, there is no configuration step.
Two things worth deciding at design stage rather than on site:
- What the chime does when Do Not Disturb is active. Most hotels suppress the audible chime and leave only the corridor indicator. Confirm this with the operator — it is a policy decision, not a technical one.
- Whether the chime sounds in the bathroom. Guests in the shower do not hear a bedroom chime. Some properties add a second sounder; most accept this and rely on the door plate indicator.
The Door Contact
The simplest device in the room. Two signal wires, no polarity — either conductor can land on either terminal. Mount the contact on the door frame with the magnet on the door leaf.
Despite costing almost nothing, this device carries disproportionate value because of what it enables.
The corridor light interlock
Configure the door contact to trigger the corridor light inside the room when the door opens.
Without it, a guest arriving at night enters a dark room and has to find the card slot by feel — the single most common arrival complaint in properties that skipped this interlock to save a small amount per room. With it, the entry area is lit by the time the door closes behind them.
Other uses for the same signal
- Energy management. Door opened plus card removed plus no motion for a set period equals room vacant; HVAC can drop to a setback temperature.
- Service status clearing. Do Not Disturb can be cleared automatically when the door is opened from inside, so guests do not leave the property with DND still showing.
- Security awareness. Door left open beyond a set duration can raise an alert at the back-end system.
None of these require additional hardware. They are logic configured in the RCU host using a signal that is already there.
Wiring Summary
| Device | Connection | Method |
|---|---|---|
| Door plate | Labelled signals to matching host terminals | Dry contact, label-to-label |
| Doorbell | Four conductors to four host terminals | Dry contact, colour-to-colour |
| Door contact | Two conductors to two host terminals | Dry contact, no polarity |
Why Dry Contact for These Devices
Even in a project where wall panels are RS485, these three devices normally stay on dry contact. There are good reasons:
- They report simple binary states — pressed or not, open or closed. A bus offers no advantage.
- Dry contact faults are contained. A damaged door plate cable does not affect anything else.
- No addressing means no configuration error at commissioning.
- Any electrician can fault-find them with a continuity tester and no software.
Mixing methods in one room is normal and causes no conflict — the RCU host has both input types.
Recommended Uses
| Application | Value |
|---|---|
| New-build hotel | Reserve 86 mm box at 1.35 m; specify door contact on every room from the outset |
| Renovation | Door plate replacement is straightforward — same box, same dry contact wiring |
| Energy management programme | Door contact signal enables occupancy-based HVAC setback with no extra hardware |
| Serviced apartments | Service status indicators reduce interruption for long-stay residents |
FAQ
Can the door plate be customised with the hotel’s design?
Yes. Room number format, panel material and colour, icon set, indicator wording and backlight colour are all specified per project.
What box size does the door plate need?
An 86 mm back box is standard. Confirm depth against the specific plate specification before the boxes are set.
Can Do Not Disturb be cleared from the front desk?
If the RCU host is connected to the back-end management system, service status can be viewed and managed centrally. This requires the network connection, not additional wiring at the door.
Can GLMZK supply door plates matched to an existing installation?
In many cases yes. Send photographs of the existing plate, the box dimensions and the host model, and we will confirm whether a direct replacement is possible.
Related Solutions
- Smart hotel RCU system
- Guest room control solution
- Hotel lighting and dimming control
- Smart hotel door plate
Contact GLMZK
GLMZK manufactures hotel door plates, doorbells, door contacts, RCU hosts and guest room control panels. We supply contractors and system integrators worldwide, with OEM design and full wiring documentation.
Send us your room type, key count and control point list, and we will return a panel schedule and wiring diagram.
Request a specification sheet and quotation | sales@smartguestroom.com