Non-linear junction detectors – A compendium of knowledge

Mini spy wiretaps and voice recorders are now increasingly difficult to detect. Technology is advancing, exposing large companies, the military and other strategic units to the leakage of valuable information. However, there is a reliable way to detect even the smallest spy device anywhere. We are talking about non-linear joint detectors. What is it?

How to detect mini spy recorders and wiretaps? It’s getting more and more difficult!

Surveillance is a phenomenon that has been around for a long time. For hundreds of years, people have eavesdropped on others to obtain valuable information on a wide range of subjects. Sometimes the relationships obtained were of key strategic importance and weighed on the fate of history, while at other times they merely brought a bit of entertainment into the lives of the nosy individuals.

Today, surveillance is intensifying. There are increasing instances of mini spy recorders being used in offices or during important military meetings, among other things.

As a result of constant technological advances, detecting ‘bugs’ is becoming increasingly difficult. Devices are becoming microscopic in size, well camouflaged and equipped with systems designed to outsmart classic detectors. 

Fortunately for the eavesdroppers, there are still non-linear joint detectors.

Non-linear junction detectors – what are they?

Non linear junction detectors (NLJD), as their specialised name in English, are devices for detecting all kinds of electronic devices, with an emphasis on eavesdropping. Due to their high price and high level of sophistication, they are mainly targeted at professional use.

Non-linear junction detectors usually take the form of handheld devices that can be used conveniently.

Importantly – the detectors are able to locate both active and passive eavesdroppers. This means that they will even discover switched-off devices – unlike most classic and cheaper solutions.

For whom are non-linear junction detectors?

Non-linear joint detectors are characterised by their high, even 100 percent, efficiency. This is because they use a number of advanced processes to accurately locate and detect unwanted devices.

For this reason, it is a very expensive solution. So, if you are concerned about a thorough search of your home because you fear that your partner is monitoring you – we advise you to equip yourself with one of the classic eavesdropping detectors.

Non-linear joint detectors are mainly intended for use by the military, law enforcement services, border guards, large companies, employers or global companies with a significant economic impact.

How do non-linear joint detectors differ from ordinary eavesdropping detectors?

Let us discuss the main differences in the operation of non-linear joint detectors and classic eavesdropping and electronic detectors. The former are devices whose operation can be compared to the way radars work. A professional instrument sends out a radio signal at a precisely defined frequency and then ‘listens’ to the reflected echo.

The returned signal, saturated with harmonics of the first signal, changes through the structures it encounters. The detector analyses it and images the level of the harmonics using the interface used. A reflected echo with a strong second harmonic will emerge from natural and a third from synthetic objects.

These signals will indicate the presence of electronic devices. Thanks to the detector sending them out independently, it will detect eavesdroppers and other instruments even when they are switched off. Their transmissivity will also be irrelevant.

The user is informed of the detection of electronics most often by sound and light signals, as well as by graphs on LCD displays.

Classical eavesdropping detectors, on the other hand, base their operation on the examination of current flows. They thus find unwanted devices at close range, but only those that are running. Standard solutions may also fail to detect ‘bugs’ hidden in walls, for example.

Eavesdropping detection… and more – what are non-linear junction detectors for?

Non-linear connector detectors are not only useful when inspecting a room for concealed eavesdropping. These types of devices will also be effective in detecting other electronics.

Non-linear junction detectors detect, among other things:

  • analogue and digital radio eavesdropping,
  • wireless microphones,
  • wireless and recording microcameras,
  • photocameras,
  • microwave transmitters
  • remote control transmitters and receivers,
  • analogue and digital voice recorders,
  • explosive detonators,
  • mobile phones,
  • smartphones,
  • SIM cards,
  • GPS locators,
  • many other electronic devices.


If you’ve ever wondered what non-linear joint detectors are for – you already know the answer. Their use goes far beyond, most popularly, searching rooms for eavesdropping.

They are devices used by professionals who can rely on them almost 100 per cent.

Which non-linear junction detectors are best? Expert advice

Which linear joint detector to choose? What should I look for? Which models are the best? Here is an overview prepared by a Detective Store expert.

Selcom ST-402 “Cayman” professional non-linear connector detector

Precise signal selection, negligible risk of misreading, response to any type of electronic device – this is how the performance of the Selcom ST-402 “Cayman” professional non-linear junction detector can be described in a nutshell.

Thanks to the user’s improved elliptical antenna design, the equipment can operate at very high sensitivity with relatively low excitation signal power.

The multi-frequency excitation mode in the 2-3 GHz band, in turn, allows even the smallest electronic components (e.g. SIM cards) to be effectively detected. Combined with enhanced audio and graph alarming, this guarantees high detection accuracy.

Also worth noting is the convenience during prolonged use.

People have bought in the last 48h!

Lornet Star hand-held non-linear joint detector

Thanks to its signal transmission over a wide bandwidth from 800 MHz to 3600 MHz and its high selectivity, the Lornet Star is able to detect the finest electronics with an accuracy of up to one metre.

The detector’s intuitive and simple operation, as well as its compact and lightweight design, guarantee comfortable operation – even for the novice user. The analysed results are displayed as clear bars on the LCD screen.

In addition, the model has a minimised effect of electromagnetic radiation on other devices in the vicinity (e.g. WiFi networks and mobile phones). At the same time, it demonstrates high selectivity and the risk of an erroneous reading is virtually zero.

People have bought in the last 48h!

  • Signal in bandwidth from 0-800 MHz or 0-2,4 GHz or 0-3,6 GHz depending on the version
  • Non-Linear Junction Detector detects miniature devices e.g. SIM cards

JJN EDD-24T non-linear junction detector

With a frequency range of 2.4 GHz to 2.425 GHz and a detection range of up to 20 cm, the JJN EDD-24T non-linear connector detector will find any electronic device by even the tiniest particle of silicon used in its manufacture.

Equipped with special algorithms, it can easily distinguish signals emitted by eavesdroppers, telephones, SIM cards, etc. from those distributed by natural non-linear connectors found, for example, in copper.

A major advantage of the JJN EDD-24T is its ergonomics. Made of aluminium, the housing provides durability and the weight of approximately 700g provides great comfort in use, even during long observations.

The built-in rechargeable battery allows more than 4 hours of continuous operation.

People have bought in the last 48h!

Non-linear joint detector Lornet 0836

The Lornet 0836 non-linear connector detector is characterised by its high sensitivity – able to detect devices from up to 15 metres away. This is due to the use of DPF dual sampling frequency technology.

The high-gain parabolic antenna – 20 dB at 3600 MHz – is also of great importance in distance detection.

Also worth noting is the built-in spot laser, which significantly improves the device’s efficiency.

People have bought in the last 48h!

Non-linear junction detectors – FAQ

Wondering what non-linear joint detectors are and how they work? Find out the answers to the most frequently asked questions!

Non-linear junction detectors – what are they?

Non-linear connector detectors are professional and sophisticated devices for detecting any electronic device, mainly eavesdroppers. They can locate them even when they are switched off or hidden in a wall.

What are non-linear junction detectors for?

Non-linear joint detectors are primarily used to effectively detect eavesdropping and other electronic devices, such as in meeting rooms. They are devices used by professionals.

How do non-linear junction detectors work?

The operation of line-junction detectors can be compared to radar. The device analyses the echoes of signals reflected from the electronics and verifies their source. The user is informed of the finding through audible alarms and graphs on the LCD screen.

Which non-linear junction detector is best?

There are many models of non-linear joint detectors on the market for professional use. You can find a wide range of such devices, along with expert reviews, at

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