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Connecting Door Entry and Intercom Systems to Your IP Phone System
A visitor presses a button at a reception door and expects an answer. The person who should answer is at a desk, not standing next to the door. Most organisations end up solving this with a separate intercom panel and a separate door release button, which means staff need two different things in two different places to admit one visitor. Connecting the intercom to the IP phone system collapses that into a single workflow on a device the receptionist already uses.
Why Intercom Belongs on the Phone System
- One device to answer: the desk phone the receptionist already knows
- One workflow: answer, verify, release the door
- No dependence on a separate intercom panel being powered or networked
- Call records tie door-entry events to a time, a location, and an extension
- After-hours routing sends door calls to whoever is on duty
How the Call Flow Works
When a visitor presses the door button, the intercom station places a SIP call to the IP-PBX. The PBX applies the same ring groups, schedules, and queue logic as an internal call. A staff member answers on a desk phone, an IP handset, or a softphone and then triggers the door release.
The release step is the security decision
The lock release should never be automatic. The platform should require an explicit action on the answering device, and the release should be time-limited so an unlocked door does not stay open. Some deployments add a second confirmation for after-hours access.
Integration Approaches
| Approach | How it works | Best for |
|---|---|---|
| Intercom dials SIP directly | Door station registers as a SIP endpoint, calls an extension | New installations with SIP-capable stations |
| Analog door phone via gateway | Door phone on an FXS port of a VoIP gateway | Sites keeping existing analog door hardware |
| Video intercom with SIP signalling | Video door station sends SIP call plus video stream | High-security entrances needing visual verification |
| Access control event integration | Badge reader triggers a call to a specific extension or queue | Offices where staff entry is badge-controlled |
Design Questions That Matter
Where does the call ring?
A single front door at a small site can ring one extension. A multi-tenant building, a hospital with several entrances, or a campus needs per-door routing with distinct ring groups, so staff know which door a visitor is waiting at before they answer.
What happens after hours?
Door phones do not stop working at 6pm. Routing needs to follow the site's operating schedule, with an after-hours destination that is appropriate for unoccupied buildings. Some sites route to a monitoring centre; others route to a mobile softphone carried by the on-duty manager.
How does visitor data get recorded?
If visitor identification is required, the call record should be able to capture who was admitted and which entrance was used. That means documenting the entry procedure and confirming that the call detail records are retained for the retention period your security policy specifies.
Multi-Site Considerations
Estate-wide door entry is where integration pays off. When each site publishes its door station as a SIP endpoint against a Redstone IP-PBX, head office can route overflow calls between sites, apply one after-hours policy across the estate, and keep a single view of door-entry call activity instead of managing each site's intercom independently.
Deployment Guidance
- List every entrance that needs call-through: main reception, loading bays, secure staff doors, car park barriers
- Decide per entrance whether visitors, staff, or both need to ring through
- Confirm the door release mechanism and whether it supports timed release
- Define after-hours and holiday routing before the system goes live
- Test a real visitor flow during peak hours, not an empty building test
Redstone IP-PBX platforms support SIP door stations and analog intercom phones through RGW series gateways, with call routing designed for reception desks, campus entrances, and multi-site estates. Redstone can map your entrances to routing, schedules, and recording requirements before installation.
Redstone Systems, Inc. founded in Delaware, USA in December 2002, has been the ODM vendor for many well-known communications companies, serving the Southeast Asian market. In 2020, Redstone Systems will begin to return to the North America market with its self-developed brand.
Redstone has a complete product line of intelligent voice gateways, providing IP-PBXs, analog VoIP gateways (FXS/FXO), digital VoIP gateways (E1/T1), border appliances, and session boundary controllers (SBCs).
With advanced technology in digital signal processor (DSP), speech coding and speech processing, as well as efficient operational tools such as cloud remote management, auto provisioning, Redstone gateways are widely used in markets of enterprise communications, cloud communications, call centers, operators’ IMS/SIP trunks, bringing users friendly, efficient and reliable communication experience.
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