An intercom is the door where a person, not a credential, decides whether to open. It puts a call button, a speaker and usually a camera at the entrance and a handset, screen or phone app inside, so a delivery, a visitor or a tenant can be identified and let in without walking to the door.
Most buildings have one or two doors that cannot be handled by a card alone: the loading gate where drivers arrive unannounced, the lobby after hours, the apartment entry where a resident has to see who is calling before they buzz them in.
The design work is deciding what the station has to do at that door — call, see, speak and release — and what happens when the network, the power or the person answering is not available.
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What a commercial intercom actually does
An intercom is a conversation and a release. The call button rings a station inside, the person answering can hear and usually see the visitor, and pressing a button releases the door. On a managed system the call, the release and the identity of the person who answered are logged, which is what turns a buzz-and-hope entry into something that can be reviewed.
That is the difference from a phone call: the intercom is anchored to a door, it knows which door, and it can open it. It is also the difference from a card reader, which cannot ask a visitor who they are.
Choose the station for the door
The door decides the hardware. A warehouse gate needs a station that people can reach from a vehicle and that survives weather, so a metal-bodied unit with a loud speaker and a clear call button is often the right answer. A lobby wants a video station at adult height with a directory and a clear picture in both daylight and after dark.
Apartment entries behave differently again: many people, a changing resident list, guests who arrive once. There, a video station with a keypad or a phone-based directory, or a system where residents answer on an app, saves the manager from reprinting a panel every month.
- Audio station where the conversation matters and the view already exists.
- Video station where the caller has to be identified before release.
- Keypad or directory where many people share one entrance.
- App-based answering where staff are not at a desk.
- Weather-rated and vandal-resistant housings on exterior and gate positions.
Door release, egress and power
The release is where intercoms meet access control and life safety. A station can hold a relay that releases a strike or a maglock, or it can hand the request to the access system so the door is opened by the same controller that governs cards. Both work; the difference is who owns the audit trail and what happens if the intercom is offline.
The hard constraint is egress. A door released by an intercom still has to let people out without a badge, and a maglock still has to fail safe on alarm. Power matters too: a station on PoE needs a switch port with the budget for it, and door hardware needs a supply that holds through the call and the release.
- Release relay at the station, or a request to the access controller.
- Request-to-exit and free egress on every controlled opening.
- PoE budget and switch ports checked before the station is ordered.
- Battery-backed lock power separate from the intercom itself.
Network, SIP and what happens in an outage
Modern intercoms are network devices. They register over SIP to a local server or to a hosted service, which is what lets a call reach a desk phone, a mobile app or a reception screen. A local system keeps working when the internet is down but the network is up; a hosted system needs the internet path to exist.
We agree the failure behaviour before the design: whether the door stays locked or releases when the network drops, who gets the call if the first station is unanswered, and whether the site needs a local fallback button. None of those are settings to discover during an incident.
Retrofitting an old handset system
Many Denver buildings still run a handset intercom with a bundle of conductors to each apartment. Sometimes that cable can be reused with an adapter; often it cannot, and the honest answer is that the station is new and the wiring is new. We test the existing cable and the door release before promising a reuse.
The bigger win in a retrofit is usually the release. An old system that buzzes but cannot prove who was let in is worth replacing for the log alone, and the new station can often share the door hardware that is already fitted.
Intercom installation across Denver and the Front Range
We install and service intercoms on the same trips as access control and cameras, from our Westminster office across Denver, Aurora, Lakewood, Arvada, Westminster, Thornton, Centennial and further into Colorado. The survey and the estimate are complimentary, and the survey is scheduled for the next business day.
Coverage, not a local office, is what the city pages claim: one crew travelling to the site, with the survey and the installation done by the people who answer the phone afterwards.
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Frequently asked questions
Can an intercom open the door by itself?
Yes, where the station carries a release relay wired to the lock. On a site with access control we usually let the intercom ask the controller to release instead, so every opening lands in one audit trail rather than in two systems.
Does the intercom need internet?
The station needs the network. A local SIP system can keep calls and releases working when the internet is down but the network is up; a hosted service needs the internet path. We agree the failure behaviour before installation rather than after.
Can we keep our existing handsets or wiring?
Sometimes. Older handset systems often use cable that the new station cannot use, and the release hardware is frequently the weak point rather than the cable. We test the runs and the door hardware before promising a reuse.
Does the intercom record video?
A video station captures the visitor at the door, and the clip can usually be stored on the platform or pulled into the camera system. Where the building already has a camera at that door, the intercom and the camera should be aimed at the same approach rather than at different angles.
What about a building with many apartments or tenants?
That is a directory problem as much as a hardware one. A keypad panel, a scrollable directory or app-based answering each solve it differently, and the right choice depends on how often the resident list changes and who administers it.