IP Intercom Not Connecting: How to Troubleshoot Door Stations and Monitors

In Depth

In Depth

When an IP intercom stops working, the fault is usually power, the network, the link between door station and monitor, SIP registration, the app account or the lock's own power supply. This guide shows how to find which one.

How an IP intercom fits together

An IP video intercom has more parts than it looks:

• an outdoor door station with a camera, call button or keypad, and a lock relay;
• one or more indoor monitors (indoor stations);
• a network switch, usually supplying PoE;
• often a phone app and the manufacturer's cloud service;
• sometimes a SIP server or PBX, such as a hotel or office phone system;
• an electric lock with its own power supply and an exit button.

This guide is vendor-neutral, with examples from manufacturers' manuals. Hikvision calls its units door stations and indoor stations and uses the Hik-Connect app. Dahua calls them VTO (outdoor) and VTH (indoor) and uses the DMSS app. Akuvox and 2N door stations are often used with SIP phone systems. Menu names vary by model and firmware, so the model selector on this page shows only the paths we confirmed.

What happens and where to look first

Power and PoE

• Confirm the switch supports the PoE standard the door station needs (usually IEEE 802.3af, or 802.3at for units with screens or heaters). An 802.3af port supplies up to 15.4 W, about 13 W at the device; 802.3at supplies up to 30 W, 25.5 W at the device.
• Do not use passive PoE injectors with standard 802.3af/at devices unless the manufacturer says it is safe. The wrong voltage can damage them.
• Check the switch's total PoE budget. Indoor monitors with screens and door stations with heaters or bright lights add up. Our PoE budget calculator does the sums.
• Keep cable runs within 100 metres and use solid-copper cable.
• Put the PoE switch on a UPS so the intercom keeps working through short power cuts.

Network, subnet and VLAN

Door stations and indoor monitors normally need to be in the same subnet to call each other directly. Hikvision's indoor station manual is explicit: with its private SIP protocol, intercom works only when the door station, indoor stations and any main station are in the same network segment.

• Check each unit's IP address, subnet mask and gateway. Our IP subnet calculator helps.
• If your network uses VLANs (for example a separate VLAN for security devices), every port used by the intercom must be in the same VLAN. A port left on the office or guest VLAN is a common mistake after a switch replacement.
• Give each unit a fixed IP address, or a DHCP reservation on the router. Akuvox's own troubleshooting notes that a door phone on DHCP may get a new address after a router reset, which breaks direct IP calls.
• If two devices share an IP address, change one. Hikvision's SADP tool lists its devices and their addresses; other makers have similar discovery tools.

Linking and numbering

Most systems link the indoor monitor to its door station by saving the door station's IP address on the monitor (Hikvision calls this the linked device settings), and give each monitor a room number that the call button or keypad dials.

• Check that the door station address saved on the monitor is current.
• Check that the room number on the monitor matches the number the button or keypad calls, and that two monitors do not share a number by mistake.
• On Hikvision systems, every device in one intercom system must use the same SIP registration password, and older units may need the "compatible with SIP 1.0" option. A changed password on one unit breaks calls to it.
• Keep door stations and monitors on compatible firmware. Update them together, using files from the manufacturer's official site.

SIP registration

If the intercom calls SIP phones, a PBX or a hotel phone system, the door station must register with the SIP server, exactly like a desk phone.

1. Open the door station's SIP status page. It should say Registered. Akuvox shows Registered or Unregistered; 2N shows REGISTERED under Status, Services.
2. Check the server address, port, extension (user) number, authentication ID and password against the PBX. SIP uses port 5060 for UDP and TCP and 5061 for TLS by default. A single wrong character prevents registration.
3. Check the PBX side: the extension exists, is enabled and is not already registered by another device.
4. If calls reach the PBX but the door station rejects some, look for call-filtering features. Akuvox, for example, has a "prevent SIP hacking" option that accepts calls only from numbers in its contact list.
5. If the PBX is across the internet or another network, NAT and firewalls can block or break SIP. Many routers have a SIP ALG feature that rewrites SIP traffic; firewall makers such as SonicWall list one-way audio, phones not ringing and dropped calls as signs it should be turned off. Check with whoever manages the router before changing it.
6. No audio or one-way audio usually means the media (RTP) traffic is blocked, or the two ends share no common audio codec.

App and cloud account

• The door station or indoor monitor (depending on the system) must have its cloud service enabled, with a working gateway and DNS, to reach the app.
• Some apps need an extra setting before they ring. Dahua's DMSS manual says you must enable alarm subscription for the VTO to receive its calls on the app.
• Find out whose account the device is bound to. If a previous tenant, owner or installer still has it, they may receive your calls, and you cannot add it. Follow the manufacturer's unbinding procedure, which may need the installer or the device's verification code.
• Use the app's device sharing to give family or staff access, rather than sharing one login.
• On the phone, allow the app's notifications and exclude it from battery optimisation. Android battery savers often stop call alerts arriving.

Plays from YouTube when you press play.

Door lock relay and power

On most door stations the lock relay is a dry contact: a switch with terminals marked NO (normally open), NC (normally closed) and COM (common). It switches the lock's power on or off and does not usually supply it, unless your manual says the unit can power a small lock directly.

• A fail-secure lock (most electric strikes) unlocks when powered. It is wired through NO and COM, so the relay closes to release it.
• A fail-safe lock (magnetic locks, which hold only while powered) is wired through NC and COM, so the relay opens to release it.
• Hikvision's 8-series villa door station manual follows exactly this pattern: NC1/COM1 is the default for a magnetic lock or electric bolt, and NO1/COM1 for an electric strike. Other models use different terminal names, so check yours.
• Check the lock's power supply output and backup battery. A failed supply is a common cause.
• Check the relay's current rating. If the lock draws more, use a separate relay or an access control power supply.
• DC lock coils should have a protection diode (many come fitted) to protect the relay contacts.

Warning Lock power supplies are usually connected to mains electricity. Do not open the power supply, the door station's back box or the lock wiring while it is powered. Leave mains connections to a qualified electrician.

Warning If a door is on a fire escape route, do not bypass, disconnect or wedge the lock to "fix" it. Escape doors must always open safely. Magnetic locks on exits need a release that cuts lock power directly and, where a fire alarm is fitted, release when the alarm sounds. We found no published Zanzibar rule that sets out escape-door lock requirements, so ask the Zanzibar Fire and Rescue Force or your fire safety adviser what applies before a lock is fitted or changed on an exit. See our access control and smart locks guide.

Weather, coast and heritage façades

Outdoor door stations face sun, rain and salty air. Use a rain hood or recess where possible, seal cable entries, and check the unit's IP rating suits the location. In Stone Town, a UNESCO World Heritage Site, visible changes to façades need approval from the conservation authority. Plan discreet units and cable routes, and check with the authority before mounting anything outside.

Before you call for help

Collect these details first:

• Brand and model of the door station and indoor monitors, with firmware versions.
• Photos of the switch port lights and of any error on the monitor.
• The IP address of each unit, if you can see them.
• The SIP registration status screen, if SIP is used.
• The app's error message and which account the device is in.
• The lock type (strike or magnetic) and whether the exit button works.
• What changed recently: router, power cut, tenant, phone.

When to call Extrion

Extrion Tech installs and supports IP video intercoms, access control, door locks and the networks they run on. See our security auditing and implementation service or contact us with your intercom model and a description of the fault.

This guide is general information. Procedures, product features and firmware change, so check your own equipment's documentation before you start.