Pitfall 4: Jamming and signal interference

This is article 4 in our series on the 6 pitfalls with alarm systems in Spain. Not a scare story — a risk salespeople rarely explain clearly: a system that does not detect interference does not protect you. It looks as if nothing is wrong.

1. What is jamming?

Jamming (signal interference) is the deliberate disruption of your alarm’s wireless link. Almost all modern systems are wireless. That makes installation easy — but your protection then depends on radio links a jammer can kill.

Three chains can fail at once:

• Sensor → hub — the hub no longer “sees” the intruder.
• Hub → siren — no noise, even if there is motion.
• Hub → phone or monitoring centre — you get no alert; a monitoring centre hears nothing. (On monitoring: Pitfall 2.)

Left: three chains work. Right: with jamming, detection, siren and alert are all broken — while the system still looks “normal”.

2. What do you notice yourself at that moment?

Picture this: someone turns on a jammer on the drive. No red light, no clear beep. The question is not what the brochure promises, but:

• Do you get a phone alert that there is interference or sabotage?
• Does a siren sound — even if the hub is briefly “deaf”?
• Or does everything stay silent — while you still think you are protected?

3. What should a good system do?

In short: detect interference, warn you, and where possible react locally (siren) — not wait for a call centre that receives nothing.

• Detection of signal loss — sensors and/or hub notice the radio link is gone.
• Alert on your phone — you see something is wrong with the connection, not only after someone is already inside.
• A siren that helps — ideally also under interference, so there is noise on site. More: outdoor siren & jamming.

How strong that protection is depends on certification level (Grade 2 / Grade 3). Explained: Grade 2 and what is Grade 3?.

4. Three questions for every salesperson

At a quote or house visit — preferably in writing:

• 1. What happens on my phone if someone jams my signal? No concrete answer? Then you know enough.
• 2. Does the siren still sound if the hub no longer has a good link? If not, one interference event can silence the noise.
• 3. Can you explain that step by step — without brochure language? An “anti-jamming” sticker alone is not proof.

5. Choose detection and alerts — not only “wireless”

Jamming is not science fiction. For a targeted break-in a jammer is a known tool. A system without adequate interference detection gives false security — especially with a monitoring centre that also receives nothing when the signal is down.

What does it mean when a jammer is active nearby? A wireless alarm system without proper interference detection can go completely silent. No siren sounds, no alert comes in, and nobody knows anything is wrong. The system looks switched on, but at that moment it does not protect you. That is exactly why your system needs to detect interference and respond straight away, with a loud outdoor siren and an alert on your phone.

During a home visit we tell you honestly what it takes to prevent a break-in at your home, using equipment suited to the job. That is why we only work with AJAX, the first brand with wireless equipment certified to Grade 3. Would you like to see how a jammer works in practice? We are happy to show you a video of our test. You can read step by step how the home visit works on our how it works page.

Want to know more about the dangers of jamming? On the page Jamming: promises and practical test you can read what happened when we tested subscription systems and our AJAX installations with a jammer. You will also find three questions to ask any seller.