Intercom and Door Entry Systems: Which Type Suits Your Property?
Updated: Oct 9
An intercom system is a door or gate panel linked to a handset, screen or phone inside, so you can speak to a visitor, and usually see them, before letting them in with a lock release. The main choice is between audio only, video, and app based systems, and then how they are wired. Blocks of flats and businesses usually add fobs or codes for residents and staff.
Which one suits you depends less on the gadgets than on three questions: who needs to get in, how far the panel is from the people answering it, and what kind of lock it has to release. Intercoms sit alongside fobs, readers and locks in the access control systems we fit, and the same questions shape both.
The main types of intercom system
There are four broad families, and most products are a mix of them.
Audio intercom. A call button and speaker at the door, a handset inside. Cheap, reliable and simple, but you are opening the door to a voice.
Video door entry. A camera in the door panel and a screen inside. You see who is there before you release the lock, and many monitors store a still or clip of each caller.
App based (IP or cellular). The panel connects to the internet over your network or a mobile signal and rings your phone. You can answer from anywhere, which suits a business or a gate at the end of a long drive.
Keypad and fob entry. No call needed for regular users. A code, fob or card releases the door, while visitors still use the call buttons.
Video door entry: what you gain
A video door entry system answers the question every audio system leaves open: who is actually at the door. That matters most in blocks of flats, offices where staff buzz in visitors, and homes where older residents want to see a caller before they open up.
Screens range from small built in monitors to full touch panels, and many systems let a second screen or a phone answer as well. If the panel records callers, bear in mind the camera may be capturing the street or a shared path. Government guidance on domestic CCTV covers video doorbells and similar devices, and data protection law applies once a camera records beyond your own boundary. Our CCTV installations follow the same positioning rules, and a video intercom is set up the same way.
Door entry systems for flats
A door entry system for flats usually has one panel at the communal entrance and a handset or screen in every flat. The panel either has one button per flat or a keypad where visitors dial a flat number, which scales better in larger blocks and makes it easier to change names.
Most blocks also want:
Fob or card readers for residents, so nobody needs a code that gets passed around. A lost fob can be cancelled on its own without changing anything else.
A timed facility for deliveries and post, which some systems offer, allowing access only during set hours.
A lock release on each handset and a clear way to open the door from inside.
An audit trail on fob systems, showing which fob opened the door and when.
Communal doors are often on an escape route, which brings in fire safety guidance. Approved Document B (England) says that where a secure door is operated by a code, keypad, card, fob or biometric reader, a security mechanism override should be possible from the side approached by people escaping. For electrically powered locks that override should be a Type A call point to BS 7273-4, usually the green emergency door release by the door, and where the building has a fire detection and alarm system the lock should also release when it operates. The responsible person for the building's fire risk assessment should agree the arrangement.
Gate intercoms
A gate intercom works like a door intercom but has to cope with distance and weather. The panel may be tens of metres from the house, so the choice is between running cable in a duct along the drive or using a wireless or cellular panel.
Cable gives the most reliable result and can carry power to the panel, but it means digging if no duct exists. Wireless links need a clear line of sight and a power supply at the gate. Cellular panels ring your mobile over the phone network, so they need a decent signal at the gate and usually a SIM plan. In each case the intercom has to be wired to the gate motor or gate lock so the release actually opens it, and the panel should be rated for outdoor use.
Wired or wireless door entry?
Wired systems are the dependable choice. Modern two wire systems run over a single pair of cores, so an older system can often be upgraded to video using the existing cable, which saves opening up walls. IP systems use data cable and can take power over the same cable.
Wireless and app based systems avoid cable runs inside the building but rely on Wi-Fi or mobile signal, and some need batteries or a monthly subscription. If the internet drops, an app only system may not ring at all, so for a main entrance we prefer a wired indoor station with the app as an extra.
Power for most intercoms comes from a low voltage power supply fed from the mains. Taking that feed from an existing circuit outside a bathroom is not notifiable under Part P. A new circuit is notifiable, so it must be installed by a registered electrician who can self-certify the work, or notified to building control before work starts.
How the door actually releases
The intercom only sends a release signal. Something on the door has to act on it, and that choice matters as much as the panel. The two common options are an electric strike, which replaces the strike plate in the frame and lets the latch open, and a magnetic lock, which holds the door with an electromagnet and releases when the power is cut.
For doors on escape routes, Approved Document B says electrically powered locks should release if the fire detection and alarm system operates, if there is loss of power or system error, and when the security override is activated. How each type behaves is covered in our post on maglocks explained, including when an electric strike suits better.
Choosing and installing the right system
When we design intercoms for homes, flats and businesses around Shifnal, Telford and Wolverhampton, the things we pin down first are:
Who enters regularly (fobs or codes) and who calls (the panel).
How many flats, rooms or answering points there are.
Whether existing cable can be reused.
The door or gate hardware and how it releases.
Fire alarm links for any door on an escape route.
Whether you want to answer from a phone as well as indoors.
If you want a system specified for your own door or gate, contact our team and we will look at the entrance, the wiring and the lock before recommending anything.
Intercom questions, answered
Can I add video to an old audio intercom?
Often, yes. Many two wire video systems run on the cable an older audio system already uses, so the job becomes changing the panel and handsets rather than rewiring. The cable has to be in good condition, which we test before quoting.
Do fob systems work in a power cut?
That depends on the lock and the power supply. Some systems have battery backup for the reader and controller. The lock behaviour on power loss is a separate question, and on escape routes guidance says electrically powered locks should release on loss of power.
Can a door entry system work with CCTV?
Yes. Many video panels can be viewed from the same app or recorder as your cameras, and a camera covering the entrance adds a wider view than the panel lens gives.
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