What Is a SIP Door Intercom, and How Do You Open the Door from the Phone?
A SIP door intercom is a doorbell with a speaker and microphone (and sometimes a camera) that connects to the phone system like an extension. Whoever presses the button at the entrance reaches a phone in the office, and you can talk to them and open the door for them with the press of a key. The ring can go to one phone, to a group of several phones, or to a mobile after work hours.
What a SIP door intercom is
An intercom is the small device next to the entrance: a button, a speaker and a microphone, and sometimes a camera. In the old intercom, it was wired to a single handset on the wall inside. Whoever wasn't standing next to the handset didn't hear it.
A SIP intercom works differently. It connects to the network, and as far as the phone system is concerned, it is exactly like an extension. When someone presses the button, the intercom "dials" the extension or group set for it, and a phone in the office rings.
What this means: any phone in the organization can answer the door. You don't need a special handset on the wall, and nobody has to sit by the entrance.
How it works, step by step
- A visitor presses the button on the intercom.
- The intercom calls the destination set for it: an extension, a group or a queue.
- The phone in the office rings. A name such as "Main Door" appears on the display.
- The employee answers and talks to the visitor, as in a regular call.
- To open the door, press a preset code on the phone's keypad. The intercom receives the code and activates the locking mechanism.
- The door opens for a few seconds, and closes by itself.
As far as the phone system is concerned, this is a regular call between two extensions. The only difference is that on one side there is a door.
Opening the door from the phone
Inside the intercom there is a relay, a small electrical switch. When the intercom receives the right code during the call, the relay closes for a few seconds and activates the door's electric locking mechanism: an electric lock inside the door, an electric strike in the door frame, or a magnet that holds the door closed.
The code is sent as keypad tones (known as DTMF), exactly like when you press a choice in an IVR menu. That is why you can open the door from any phone that can send tones: a desk phone, a cordless handset, and even a mobile, if the call was transferred to it.
On advanced phones you can program a dedicated "Open Door" key that presses the code for you. This is convenient for a secretary who opens the door dozens of times a day.
What if someone presses the code by mistake in the middle of another call? It won't open the door, because the code only works during a call with the intercom itself. So you can choose a short, convenient code, as long as it isn't known to everyone who walks by.
Ringing a group
The real strength of a SIP intercom is the flexibility of its destination. Instead of ringing one phone, it can ring a hunt group: several phones together, or one after another.
For example: the button at the entrance rings the secretary's office first. If there is no answer within ten seconds, it also rings the administration and the teachers' room. And if there is still no answer, it rings the building caretaker. That way, a visitor isn't left outside just because the secretary stepped out for a moment.
You can also combine time-based routing: during work hours the door rings in the office, and in the evening and at night it rings the guard, the caretaker or the mobile of the person in charge. The intercom itself doesn't change; only the destination in the phone system.
Another option is to send the ring from the door to a queue, like a regular incoming call. This suits a place with many visitors, where several employees share answering and you want the ring to always reach whoever is free.
An intercom with a camera
Many intercoms come with a camera. So when someone presses the button, you can not only hear them but also see who is standing outside, before you open.
To see the picture, you need something that displays it: an IP phone with a screen that supports video, a dedicated indoor screen that comes with the intercom, or an app on a computer or mobile. On a regular phone without video, the call will work, just without a picture.
Note: a camera at the entrance is also a security camera for all intents and purposes. Check where the picture is saved, if at all, and who can view it. In any case, aim it only at the area of the door.
A camera helps even when the call is short: a courier who says "delivery" sounds the same as anyone else, but in the picture you can see whether he is really holding a package. In educational institutions, it is a convenient way to verify that whoever asks to come in is really a student's parent.
Types of intercoms
| Type | What it includes | Best for |
|---|---|---|
| One button | Button, speaker, microphone | An office or institution with one entrance |
| Several buttons | A button for each department or office | A building with several organizations |
| With a keypad | Keys for entering an access code | Employees who come in without ringing |
| With a card reader | Entry with a card or tag | An institution with many employees |
| With a camera | Video to a phone or screen | Anywhere you want to see before you open |
Many IP phone manufacturers also make intercoms, and a few companies specialize only in this. What matters is that the intercom supports SIP, so it connects to the phone system like an extension.
Power, lock and electrician
Most intercoms get power through PoE, meaning from the same network cable. But the electric lock is a different story: it needs its own power supply, and connecting it to the intercom's relay is a job for an electrician or an access-control installer.
An important question when choosing a lock: what happens in a power outage? One type of lock stays locked without power, and another type opens. On a door that is also an emergency exit, this has safety implications, and sometimes there are fire department requirements. This decision is made with a certified installer.
And if you want the intercom to keep working in a power outage, connect the switch and the lock's power supply to a UPS.
Location and installation
An intercom stands outside, in rain, sun and dust. So choose a model designed for outdoor installation, with a water and dust resistance rating (marked with the letters IP and two digits, for example IP65). At an entrance with a lot of traffic, or where damage is a concern, there are models with a strong metal housing.
Height matters: the button should be reachable for a short person, a child or someone in a wheelchair, and the camera should be at an angle that sees faces and not just a hat. Next to the button, a clear sign is a good idea: "Press to ring the office."
Finally, a network point: a network cable has to be run to the intercom. Wi-Fi is not suitable here, since a door is exactly the place where you don't want an unstable connection.
At a noisy entrance, near a road or a playground, choose an intercom with a loud speaker and a noise-filtering microphone, otherwise the conversation with the visitor turns into shouting.
Security
An intercom that opens a door is part of the building's security system, so treat it seriously.
- An opening code that is not too simple (not 1, not 1234), and that is not shared with all employees.
- Change the default password of the intercom's management interface.
- Connect the intercom to the network in a way that prevents access to it from outside, and in larger places, on a separate network (VLAN).
- Restrict the code so that it works only during a call from the intercom, and not from anywhere.
Also pay attention to routing: if outside work hours the door is forwarded to a mobile, whoever holds that mobile can open the door from anywhere. This is convenient, but it has to be a person who is responsible for it.
Old intercom vs. SIP intercom
| Old intercom | SIP intercom | |
|---|---|---|
| Where it is answered | One handset on the wall | Any phone in the organization, or a group |
| Wiring | Dedicated wires to the handset | A regular network cable |
| After work hours | No one answers | Can be routed to a guard or a mobile |
| Open | A button on the handset | A code or key from any phone |
| Changes | Electrician | Changing the destination in the phone system |
A real-world example: a talmud Torah with a gate to the yard
At the "Sha'arei Chaim" talmud Torah (a fictional name), there was a gate to the yard with an old bell that rang only in the office. In the morning hours this worked, but at noon, when the secretary stepped out, parents waited outside for long minutes.
The bell was replaced with a SIP intercom with a camera. During school hours it rings the office first, and after ten seconds also the teachers' room and the building caretaker. After school ends, the ring goes to the guard's cordless handset.
The gate is opened by pressing a key on the phone. Parents no longer wait, and the secretary doesn't have to run to the gate.
In addition, every ring from the gate is now recorded in the call log as a regular call, so you can see how many times it rang during the day and when traffic was heaviest.
Before you order: a checklist
- How many entrances? Each entrance needs its own intercom and a network point.
- What lock do you have today? Is it electric, and what happens to it in a power outage.
- Who answers, and when? A list of phones for work hours, and a list for the evening, night and days off.
- Do you need to see? If so, an intercom with a camera and phones or screens that display video.
- Who comes in without ringing? If employees enter with a code or a card, choose a model with a keypad or a reader.
- Where will it stand? In sun, in rain, at an accessible height, with a clear sign.
With the answers to these six questions, choosing a model and setting it up in the phone system become simple.
How it works with us at Kesher
An intercom that supports SIP connects to the phone system like an extension, and appears on the Extensions screen in the control panel. From there you set, as for any extension, what happens when there is no answer.
You build the ring destination with the control panel's regular tools: layered hunt groups (first the office, then more phones) and time groups, so that in the evening the ring goes to the guard or the person in charge.
On the Call Route screen you can see in a diagram where a ring from the door goes at any hour, and make sure there is no "hole" where nobody answers.
The electric lock and its connection to the door are installed by an electrician or an access-control installer. We are here to coordinate the phone system side, and a real person answers any question.
FAQ
Can I open the door from my mobile?
Yes, if the ring from the door is forwarded to the mobile and the mobile sends keypad tones. You enter the opening code during the call.
What happens when nobody answers the door?
It depends on the setup. You can ring a larger group, forward to a mobile, or play a message. Check that there is no hour when the ring reaches nobody.
Do I need a special phone to see the camera?
To see video you need a phone with a screen that supports it, a dedicated indoor screen or an app. On a regular phone you can only hear.
Can I connect our old intercom?
An old intercom that does not support SIP cannot connect directly. Usually the outdoor unit is replaced, and sometimes the existing lock can stay.
Who installs the lock?
An electrician or an access-control installer. It is work on electricity and the door, and not part of setting up the phone system.
For how long does the door open?
This is set in the intercom's settings, usually a few seconds. It can be extended if the door is heavy or far away.
Can I have several entrances, with an intercom for each?
Yes. Each intercom is a separate extension with its own name, so the display shows which entrance is ringing.
Does the intercom work in a power outage?
Only if the switch, the router and the lock's power supply are connected to a UPS. Otherwise it goes off.
Can employees come in with a code without ringing?
With an intercom that has a keypad or a card reader, yes. This is set in the intercom itself.
How do I know the ring came from the door and not from a regular call?
The intercom has its own name, for example "Main Door," and it appears on the display. On many phones you can also set a different ringtone for it, so you hear right away that it is the door.