A mobile SIM in an intercom fails in ways it never would in a phone. It expires because nobody called it. It runs out of credit on a Friday night. It picks up a marketing text the module cannot handle and stops answering.
We make SIM cards that do one thing: keep gate intercoms and door entry systems answering calls. No top-ups, no expiry from sitting idle, and no guessing which network to pick — our AI model does that part.
Over 12,000 SIMs deployed across the UK
Most intercom SIMs lock you to whichever network you happened to order. If that network is weak at the gate post, the intercom is weak at the gate post, and you find out after it is installed.
Our GSM SIMs carry EE, O2, Three and Vodafone. Our AI model reads signal conditions at the location and connects to the strongest available network, then keeps checking. You do not choose a network, and you do not need to know which one is best at your postcode. That is the point.
It matters more than people expect. A gate sits at the property boundary, usually the furthest point from the house, often behind trees or a wall. Signal at the kitchen window tells you very little about signal at the gate.
Our Data-Only plan runs on a fixed Vodafone connection rather than Smart-Switching — see below.
Pay-as-you-go SIMs disconnect after a stretch without chargeable use. A dial-to-open gate only ever receives calls, so the network reads it as dormant and cuts it off. Holiday homes and rural properties go down first.
Nobody watches the balance on a gate. You discover it when the gate stops opening.
Networks push texts and picture messages to consumer SIMs. Some intercom units lock up when one arrives.
No fallback if coverage at the gate is poor.
Our SIMs are built for equipment that sits still and waits. They stay live on inbound calls alone, marketing traffic is off, and they move between networks rather than betting on one.
Pick by how the intercom behaves, not by price.
You ring the gate from an approved number, it rings once and hangs up, the gate opens. No conversation. Your phone becomes a remote control with unlimited range.
Choose this if nobody needs to speak to visitors. Common on private driveways, farm entrances and holiday properties.
A visitor presses the button, your phone rings like an ordinary call, you answer and speak to them, then release the gate.
Choose this if you need two-way conversation. This is what most residential door entry systems use.
For app-based and video intercoms. If the unit sends video to your phone like a FaceTime call, or reports to a cloud service, it needs data rather than a voice line.
Choose this if the intercom uses an app, video, IP or cloud. Do not choose a GSM plan for these units — they will not work.
Not sure which one? Send us a photo of your intercom, or tell us the make and model. Our technical team will tell you which plan it needs before you spend anything.
Most "the SIM doesn't work" calls are not SIM faults. They are one of these five, and all of them take two minutes to check before you leave site.
Dial-to-open works by the intercom recognising the number calling it. If the caller's number is withheld, the intercom sees an unknown number and refuses to open. There is no error message — the gate simply does nothing while the phone rings normally.
Check every authorised handset has caller ID switched on. On most UK networks a withheld number can be forced through by dialling 1470 before the gate number, which is a quick way to prove this is the fault.
This is the single most common cause of "it worked at the workshop but not at the house".
A SIM asking for a PIN on power-up will never register. The intercom cannot present a PIN, so the module sits there looking dead.
Ours ship with the PIN disabled. If you are moving a SIM in from elsewhere, put it in a phone first, turn the PIN request off, then fit it. Our SIM install guide walks through it.
Standing at the gate with a phone showing four bars tells you very little. Bars are a marketing abstraction and every handset scales them differently.
Do it properly:
Test in the position the unit will actually sit. A metal gate post, brick pillar or recessed housing can cost 10–15 dB on its own. Our signal checker gives you a starting point before you travel.
Signal also changes with the seasons. A gate installed in February under bare trees can lose usable signal by July.
Across the 61 SIM-capable intercoms we document: 29 take nano (4FF), 17 standard (2FF), 10 micro (3FF).
Our SIMs ship multi-cut so they fit all three. But knowing which you need matters when you are cutting on site: once you have punched a 2FF down to nano, it does not go back.
Power the unit, wait for it to register, then make one call in each direction the system supports. Dial-to-open: ring the gate from an authorised handset and confirm it triggers. Two-way: press the call button and confirm the conversation works both ways, not just one.
One-way audio is usually a wiring or volume fault rather than a SIM fault, and it is much cheaper to find while you are still standing there.
Vodafone, EE and Three have shut down their 3G networks. O2's is under way. A large share of GSM intercoms installed over the past fifteen years were built for 2G or 3G only, and when the network they rely on goes, the unit simply stops. No error, no warning, nothing physically wrong with it.
Two questions decide whether a new SIM helps:
Model names are not a reliable guide either. Several manufacturers sell a "4G" badged unit whose radio module varies by production run, so what is printed on the enclosure does not always match what is inside.
If your unit is not compatible, we will tell you that rather than sell you a SIM that cannot solve the problem.
We hold installation documentation and SIM setup notes for 110 gate and intercom systems across 41 manufacturers, 61 of which take a SIM — Videx, CAME/BPT, BFT, AES Global, Comelit, Bell System, Nortech, King Pigeon, Tador and more.
So we can tell you where the SIM slot sits, what form factor it takes, what the module actually supports, and what usually goes wrong on the first test call.
Tell us the make, model and where possible the module part number, and we will confirm what it supports before you order anything.
Cancel any time with 30 days' notice.
If you fit gates and intercoms for a living, a trade account changes the maths on every job.
Trade pricing, pre-activated stock, your own end-customer pricing, and a mobile app covering every SIM you have ever fitted. A SIM stops being a line on the invoice and becomes monthly recurring income.
It also saves van journeys. When a customer calls to say the gate has stopped opening, you can check SIM status before you get in.
Most will physically fit. The problems come afterwards: expiry from inactivity, credit running out, network marketing messages jamming the module, and no fallback if coverage at the gate is poor. Intercoms are static equipment that sit idle for long stretches — the opposite of what a consumer phone SIM is built for.
On our GSM plans you do not pick one. The SIM carries EE, O2, Three and Vodafone, and our AI model connects to the strongest available network for that location. The Data-Only plan is fixed to Vodafone.
The most common cause is caller ID being withheld on the calling handset — the intercom cannot recognise an unknown number, so it ignores the call. Try dialling 1470 before the gate number. If it opens, caller ID is your problem.
A SIM on a plan built around receiving calls rather than making them. You ring the gate from an authorised number, the intercom recognises it and opens without answering. Because the SIM only ever receives, it needs a plan that will not disconnect it for having no outgoing activity.
Only if it uses it. Audio-only intercoms need voice, plus SMS for programming. Video intercoms, app-controlled entry and anything reporting to a cloud dashboard need the Data-Only plan. If you are unsure, send us the make and model.
Only if the intercom supports 4G. If the module is 2G or 3G only, the hardware itself needs upgrading. Tell us the make and model and we will say which applies before you order.
Better than −85 dBm measured at the aerial position is comfortable. Between −85 and −100 dBm it will work but may suffer in wet weather and summer foliage. Below −100 dBm expect intermittent failures.
It varies. Across the 61 SIM-capable intercoms we document, 29 take nano (4FF), 17 take standard (2FF) and 10 take micro (3FF). Ours ship multi-cut so they fit whichever the unit needs.
30-day rolling, billed monthly in advance. Cancel any time with 30 days' notice.
On the GSM Talk plan each call is capped at around three minutes — enough to speak to a visitor and let them in, and it stops a line being left open by accident.
Tell us what you are fitting, or pick your plan and we will ship it ready to work.
Fair usage policy applies. LynixSIM plans are designed exclusively for gate and intercom systems and are not intended for general mobile use. Each SIM covers one single private residence or self-contained dwelling. SIMs are for UK use only and are not a replacement for a normal phone line — do not rely on them for emergency calls. GSM plans include 20 SMS for installation and programming, then 12p per SMS. See our Terms & Conditions for full details.