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Mobile phone intercept scanner

Kolibrie was a car-phone intercept receiver developed by the Politie Verbindingsdienst (PVD) (Police Signals Service) in The Netherlands in the early 1990s. It was intended for the interception of criminal conversations on the Dutch NMT-900 cellular network, known as ATF-3. Kolibrie is Dutch for Hummingbird. The use of Kolibrie lead to some debate during the public hearings of the Van Traa Commission in 1995. It was gradually phased out when GSM became popular.
The mobile telephone networks that were used between the 1970s and 1990s were all based on analogue duplex radio systems. Eavesdropping by means of an ordinary (computer) scanner was very easy in those days, not only for hobbyists and criminals, but also for police investigators.

The problem with an ordinary radio scanner was that the later 900 MHz networks (NMT-900 or ATF-3) had 2000 channels, making it difficult to determine the right channel. Furthermore, the eavesdropper would lose the signal when the mobile station moved from one cell to another.
Front panel of the Kolibrie, with the unique ID plug

In order to overcome these problems, the Police Signals Service (PVD) developed Kolibrie: a purpose-built scanner that was able to intercept the mobile telephone (MT) and the base station (BS) simultaneously, and follow these signals when they moved from one channel to another.
At the time, the analogue mobile phones had a built-in AFSK modem that periodically contacted the base station in order to setup a call and/or negotiate a hand-over from one cell to the next. During a negotiation, the voice channel was briefly muted. Kolibrie was able to interpret the negotiation data and follow the hand-overs at the edge of a cell. Furthermore, it was able to display the number of the caller and the callee.

The image on the right shows Kolibrie receiver with serial number NL127 in its typical blue case. It is internally stamped 09 December 1992.
Kolibrie scanner (KOL3)

The police was aware of the 'grey area' of intercepting mobile conversations [5]. Although strictly speaking it was not illegal in The Netherlands to use a radio scanner, doing so by means of a Kolibrie made it possible to follow specific phone numbers and people (much like a phone tap). In order to protect the units against anauthorized use, and to prevent them from falling into the wrong hands, a unique key in the shape of a 3 mm jack plug was needed to operate the device.

It is currently unknown how many Kolibrie scanners were produced, but each of the 25 police districts in The Netherlands had at least 2 units. Taking into account that some extra receivers may have been produced for other agencies and for the PTT (the Dutch telecom operator), and perhaps even for some foreign 'customers', a safe estimate seems to be around 100 units.

Today, the Kolibrie is a highly wanted collector's item. After the units were phased out in the late 1990s, they had to be destroyed, but some units showed up on official government sales in the early 2000s and were subsequently bought by surplus houses. As most buyers didn't known what they were (there is no name tag), most units were destroyed or dismantled and used for parts.
Samsonite briefcase Kolibrie inside storage case Front panel of the Kolibrie, with the unique ID plug Kolibrie scanner (KOL3) Front panel of the Kolibrie scanner Remote Control Identification plug

Operating the Kolibrie is extremely simple and doesn't require any special training. After switching it on with the ON/OFF switch at the left, it briefly shows the current version number and then promts for the Identification Plug (KEY) to be inserted. Once the key is inserted, the unit shows the serial number (e.g. NL127) and then waits for the key to be removed.

Front panel of the Kolibrie scanner

The unit is then ready for use and will start scanning the NMT-900 frequencies of the mobile station (890-915 MHz) that should be in the vicinity of the interceptor. In case there are many mobile stations in the area, it might be necessary to set the attenuator to LOW and adjust the squelch (SQL) so that only the observed station (i.e. the subject under surveillance) is picked up. If it locks onto the wrong conversation, the SEARCH button should be pressed find the next one.

When scanning, the display shows the text BANDBEWAKING (Band Monitoring). Once the unit is locked onto the desired channel, the display shows Gesprek gevonden (Conversation found) and the attenuator can be switched off again (HIGH), so that the conversation can be caught properly. In the above image, the upper line of the display shows a series of dashes. As soon as a (digital) negotiation signal is caught, this line shows the number of the caller and the dialled number.

When driving around, the radio signal strength indicator (RSSI) gives an indication of the distance to the subject under observation. When Kolibrie looses the MT signal, the display shows Gesprek verloren (Conversation lost), but stays on the channel as long as the BS signal is present.

Working Kolibrie showing the reception of an MT and BS signal

Two LEDs at the right show whether the MT and BS signals are present. As the volume of the intercepted mobile phones varies significantly, a potentiometer (BAL) allows the audio balance between the MT and BS channels to be adjusted so that they both sound equally strong.
All connections, except for the unique ID key, are at the rear of the unit. Kolibrie is powered by a 12V DC voltage, such as the battery of a car. Is was generally connected to the cigarette lighter receptacle of a vehicle. The 12V DC source is connected to the 3-pin XLR socket at the right.

Rear panel of the Kolibrie scanner

The female XML socket at the top left is used for the connection of a speaker, such as the one that was supplied with the kit. Below the XLR socket is a 3 mm jack socket for the connection of headphones. The antenna is connected to the BNC socket at the top center, left of the two line outputs (one for each receiver). A remote control unit could be connected to the large 25-way D-type socket at the center. It allowed unobtrusive control from, say, the dashboard of the car.

The vertically mounted 15-way D-type socket (here marked as EXT) was provided for the connection of additional equipment, such as automatic recording devices and personal computers (PCs). Recording equipment can be connected either to the two CINCH (RCA) sockets or to the 15-way D-type socket (EXT). When using a stereo recorder, the MT and BS channels can be recorded separately (L and R). This allows better analysis of the (criminal) conversation later.

Although we are not certain about this at the moment, we have the impression that the 15-way EXT socket also carries a serial port that allows the internal microcontroller to communicate with an external computer, such as a PC. It can be used for targetting specific phone numbers.
Front panel of the Kolibrie scanner Rear view of the Kolibrie Close-up of the Radio Signal Strength Indicator (RSSI) Identification plug (unique ID) mounted at the front panel Identification plug Conversation found RSSI indicator and display Connecting the necessary cables at the rear

Kolibrie was suitable for use in a car as well as from a desktop. In any case it was powered from a 12V DC source. When used in a car, the unit was powered from the cigarette lighter socket. When used on a desktop is was generally powered by an external power supply unit (PSU). For the 25 police districts, Kolibrie was supplied in a sturdy plastic Samsonite briefcase, as shown below.
Samsonate briefcase for storage and transport of Kolibrie Briefcase External 8 ohm speaker with XLR connector Speaker 900 MHz magnet-mount antenna Antenna Remote control unit with display and push-button Remote 25-way D-type extension cable for connection of the Remote Control unit Cable 12V DC power cable with cigratte lighter plug Power Unique ID plug (individually paired with each Kolibrie unit) ID Plug

For transportation, Kolibrie was usually stored inside a sturdy unobtrusive plastic Samsonite case, together with all accessories, cables and the ID plug. The Kolibrie, the antenna base and the cables are stored in the bottom section.

The actual antenna rod, the speaker and the remote control unit are stored in the top half of the case. Some Kolibrie units have two Velcro strips at the upper side, so that they could quickly be installed inside an unmarked car.
Kolibrie inside storage case

Kolibrie does not have an internal speaker, so an external one is needed in order to monitor the intercepted sound without using headphones.

A standard Antiference speaker, such as the ones commonly supplied with mobile phones, came with the Kolibrie. It should be connected to the female XML socket at the rear. Although the speaker could be mounted at the dashboard, it was generally 'floating around' somewhere.

A suitable antenna should be connected to the BNC socket at the rear of the Kolibrie. As such antenna's were generally not available on an unmarked police car, a 900 MHz magnet-mount antenna was supplied with the kit.

The mount and the fixed cable were stored in the cable compartment of the Samsonite case, whilst the antenna rod itself was stored in the top half. Magnet-mount antennas did not attract unwanted attention as they were frequently used with car phones at the time.

Remote Control
Although Kolibrie is small enough to be used inside a driving vehicle, it was sometimes more practicle to hide it from view and use the remote control unit that consists of a small plastic box with a display and a push-button. It is connected to the rear of the Kolibrie via a common 25-way D-type printer extension cable.

The display is connected in parallel to the existing display and the push-button duplicates the SEARCH button at the front panel. Turn the Kolibrie off when connecting the remote control.
Remote Control

12DV Power Cable
Kolibrie is powered by a 12V DC source, such as the battery of a car. When using the device inside a vehile (which was generally the case), it was connected to the cigarette lighter receptacle at the dashboard.

A suitable cable, with a female XLR plug at one end and a cigarette lighter plug at the other end, was supplied with the kit.
12DC Power cable with cigarette lighter receptacle

Identification plug
To avoid unauthorized access to the Kolibrie, each device comes with its own unique key in the shape of a 3 mm jack plug that is attached to a key ring. Inside the plug is a unique ID chip, like the Dallas DS2400 or the later Maxim DS2401 [3], without which the device can not be used.
After switching on the unit, the key has to be inserted momentarily. The device only continues if the key matches the internal serial number of the Kolibrie. This way, any lost or stolen devices will become useless. Once Kolibrie has seen the correct serial number, the user is prompted to remove the key, so that a key is never left inside the unit. Very useful in case Kolibrie gets stolen.

Some Kolibrie units have popped up on the surplus market without a matching key and the question has arisen whether it would be possible to create a working key or an emulation for it.
Identification Plug

Finding the appropriate DS2401 chip with the correct serial number inside, is impossible as the manufacturer (Dallas, now: Maxim) guarantees that no two ID chips have the same serial number and there are no (programmable) alternatives from them or from any other manufacturer. In practice, when a police investigator lost his key, Kolibrie had to be reprogrammed by the PVD.

Pinout of the Dallas DS2401 unique ID chip

Although it would theoretically be possible to build an emulator based on a small microcontroller, such as a Microchip™ PIC, it would be virtually impossible to 'guess' the required number, as it is hard-coded into the firmware of the Kolibrie and bears no relation to the serial number printed at the rear of the device and on the key. Furthermore, the ID-numbers were issued randomly by the manufacturer, and the firmware inside the Kolibrie's microcontroller is protected against reading.

To cut a long story short: a Kolibrie without the matching key is useless.

Kolibrie inside storage case Cables stored inside the briefcase Remote Control 25-way D-type extension cable Start searching again The remote control unit stored inside the lid of the briefcase Identification plug

Kolibrie exploded view

Opening the Kolibrie is fairly simple. The case consists of a frame in which all PCBs are mounted, a front panel, a rear panel, and two blue case shells. After removing the 4 screws at each side, the two case shells can be removed and the surprisingly modern well-designed interior is revealed.
Determining the age of the receiver is rather difficult, as the text has been removed from most of the ICs. However, the ICs that do carry manufacturing codes, have all been built in 1991 and 1992, and a stamp at the bottom of the PSU board reveals it was tested on 9 December 1992.

The markings on the edge of the PCB suggest that the receiver was developed in-house by the PVD in Bilthoven (Netherlands). They also show that the internal name for the receiver was KOL3. This could mean that it was the third design, or that it refers to the ATF-3 network.
Kolibrie interior

As the PCB is also marked 'Issue 2' it seems likely that KOL3, refers to the ATF-3 network (NMT-900). Although some documents suggest that there was also a Kolibrie for the older ATF-2 network (NMT-450) we have not (yet) found any evidence for the existence of a KOL2 device.
Kolibrie consists of three large PCBs that hold the CPU and the receivers, a smaller one with the PSU and the Audio Amplifier, and some smaller PCBs mounted behind the front panel. After removing the top cover of the blue case, the upper board (marked PCB2) becomes visible.

This board contains the CPU that is built around a Motorola MC68HC705 microcontroller [7]. It is part of Motorola's HC05 family and contains an additional serial I/O port, which is probably used for communication with a Personal Computer (PC) that can be connected to the EXT socket.
The CPU on the upper board (PCB2)

The upper board also contains the input band filters, HF amplifiers and the first VCO-based mixers. The VCO is under control of the CPU and allows scanning over the full 25 MHz frequency span. From the upper board, HF signals are distributed to the two receivers (MT and BS) below.
The two receivers are largely identical, but each one covers a different frequency band. The Mobile Telephone receiver (MT) covers the 890-915 MHz band (also known as the uplink), whilst the Base Station receiver (BS) covers the 935-960 MHz band (also known as the downlink).

Furthermore, the MT receiver contains additional electronics to control a signal strength indicator (SSI) in the shape of a 16-unit LED bar mounted at the front panel. In order to intercept only strong (nearby) signals, an attenuator can be used when searching the spectrum (HIGH/LOW).
PCB1 - The MT receiver

The lower board contains the BS receiver, which has neither a signal streng indicator nor a switchable attenuator. The MT receiver is used for detecting an intercept candidate, whilst the BS receiver just follows. A small PCB is mounted behind the other three boards, behind the rear panel of the unit. It contains the Power Supply Unit (PSU) and the LF Audio Amplifier.
Opened Kolibrie Kolibrie interior Kolibrie interior Top view of the Kolibrie interior Kolibrie on its side Bottom view Bottom view of the front panel View of the interior from the left side
Kolibrie interior, with PCB2 removed Kolibrie interior The CPU on the upper board (PCB2) PCB2 holding the front-end (bottom left) and the CPU Local oscillator with VCO PCB1 - The MT receiver Rear view of the front panel PSU and Audio Amplifier mounted behind the rear panel
Identification Date stamp at the bottom of the PSU/LF board The upper board (PCB2) with CPU and front-end Input band filter (BS) and pre-amplifier Input band filter (MT) and pre-amplifier Bottom view of PCB2 (CPU and front-end) TDA1516Q 2 x 12W LF stereo power amplifier Red paint on the screws to spot that the case has been opened

As the Kolibrie was a 'sensitive' device, several measures were taken to prevent misuse and tampering. The following ant-tamper measures can be observed:
  • Identification plug
    Each Kolibrie is paired with a matching unique-ID plug that is used as the key. Without the proper key, it can not be used. More...

  • Red painted screws
    The eight screws that hold the two case shells together, are marked with red paint, in order to make it self-evident that the case has been opened.

  • Text removed from the ICs
    In order to prevent reverse-engineering, the identification numbers have been removed from nearly all ICs and even from the reed relay.

  • Read-protected microcontroller
    The Motorola microcontroller has a built-in 7KB EPROM that contains the firmware, the unit's serial number and the unique-ID number. After programming, a security bit (SEC) is set to protect the EPROM against reading/dumping from the outside.

  • Lackered PCB solder side
    The bottom side of the three main PCBs is covered by a hard dark-green sealing. This protects the PCB against moist, but also makes any modifications self-evident.

Block Diagram
The diagram below roughly shows how the Kolibrie scanner worked. The unit has two receivers: one for the reception of the mobile telephone (MT) and one for the base station (BS). As the frequency distance between the MT-channel and the BS-channel is always 45 MHz, the two receivers are operated in parallel. The antenna signal is first filtered for the appropriate band (890-915 MHz and 935-960 MHz), then amplified and then mixed with the signal from a local oscillator, which is a VCO operating between 813-838 MHz under control of the CPU.

Block diagram of the Kolibrie scanner

After mixing, the individual signals (77 MHz and 122 MHz) are fed into the individual MT and BS receivers. When scanning, the MT receiver is the leading one. Once it has picked up a signal, it will cause the CPU to stop scanning. A vertical LED-bar will show the signal strength of the mobile station and the BS receiver will be tuned to the corresponding base station channel, so that both can be heared simultaneously. As the strength of the audio signal varies between stations, a potentiometer (BAL) can be used to adjust the audio balance between the two signals.

The audio signals are available at the rear of the unit, either mixed, or as individual signals, to allow recording. For the latter a potential-free contact from a reed-relay is available as well. It could be used to automatically start a tape recorder on reception of a signal.
ATF-3   NMT-900
ATF (AutoTeleFoon) was the common name for the Dutch analogue mobile (car) phone network that was introduced in 1980. The first network operated at 150 MHz and was known as ATF-1. It was used in The Netherlands, Germany and Austria. Because of the rather low frequency, the cells of the network were very large, requiring a lot of (transmission) power, and limiting the maximum number of users to approx. 2500 in The Netherlands. After 3 years the network was exhausted.
ATF-1 was followed by ATF-2 in 1985. It was more affordable than ATF-1 and was based on the Scandinavian NMT-450 standard [2]. This network operated on 450 MHz and had smaller cells, allowing more simultaneous users. In the Netherlands the capacity of the ATF-2 network was approx. 50,000 subscribers, which was reached just four years later, in 1989.

The capacity of the network was expanded by the introduction of ATF-3 in 1989. It was based on the NMT-900 standard [2], featuring 1999 channels and full duplex voice transmission.

ATF-3 used a downlink in the 935-960 MHz band and an uplink in the 890-915 MHz band. Due to the higher frequency (resulting in smaller cells) and the increased number of channels, ATF-3 allowed more subscribers than ATF-1 and ATF-2. As a result, ATF-3 was more affordable and it wasn't before long that it became popular amongst business men, but also amongst criminals.

As ATF-3 was an analogue network, using no encryption whatsoever, it was relatively easy to intercept a conversation using a simple radio scanner. Users were warned for this by means of a text printed on the inside of the handset:

U voert een gesprek via een radioverbinding. Afluisteren is mogelijk.
(You are communicating via a radio channel. Eavesdropping is possible).

Eavesdropping became impossible, or at least extremely difficult, when the GSM network was introduced in the mid 1990s. Being a fully digital system, GSM uses advanced cryptographic techniques to secure the conversation. In the Netherlands, GSM was rolled out from 1994 onwards and gradually replaced the ATF-3 network. ATF-3 was finally closed down in 1997.

In some other countries, the NMT network survived a bit longer. In Norway and Finland, the NMT network was operational until 2004 and in Sweden even until 2007 [2]. In Russia, the last NMT service was suspended in 2008 and Iceland was the last to close down their NMT service in 2010.
When investigating serious crimes, it is relatively easy for the Dutch Police to obtain a warrant for a telephone tap. This was already the case in the late 1980s and criminals were very much aware of this. As a result, they less and less used their land-lines for criminal conversations and increasingly started making use of mobile phones. Although it was relatively easy to intercept an (analogue) mobile telephone conversion, it was obscured by the sheer number of channels and criminals did not expect the police to be technically capable and/or equipped for the task.

The police noticed the increased use of mobile phones by criminals and started looking for ways to intercept their conversations. Although the intercepted information could not be used directly in a criminal case without a warrant, it gave them a good indication of wheather they were 'on the right track'. Furthermore it allowed them to follow a car at a larger distance than usual.

Standard radio scanners were available in the Netherlands from the early 1970s onwards from any electronics shop in the country, eventually succeeded by the first generation of computer-based scanners. Although the scanners of the early 1990s covered the 900 MHz band, scanning the 2000 channels of the ATF-3 network was not very practicle, especially when the target was driving around and, hence, changed channels frequently, as illustrated in the drawing below.

For this reason it was decided to let the Police Signals Service (PVD) develop its own proprietary scanner that would take the pain out of finding and following the right conversation. It is believed that the first Kolibrie devices entered service in the early 1990s. As the police didn't want to give away their new tactic, the existence of the Kolibrie was kept secret and the device was never mentioned in their official reports (Dutch: proces verbaal). It was thought that criminals would move to other means of communication once they knew their conversations were overheard.

Officially, the information that was captured this way, could not be used in a court case, unless a warrant was issued prior to the interception. Nevertheless it gave them good clues as to the feasibility of a case. The police thought it was admissable as the information could have been intercepted by anyone by means of an ordinary radio scanner. Furthermore, the mobile phone user (i.e. the criminal) knew his conversation could be overheard as he was pre-warned by a message printed inside the handset. On the other hand: Kolibrie made it possible to trap a specific phone number, making it a targeting investigation tool. All in all a 'grey area'.

All this changed when the methods of the Police's Inter-Regional Investigation Teams (IRT) were publicly investigated in the mid-1990s, and the investigators were forced to reveal the existence of the Kolibrie. Luckily it didn't cause much harm as most criminals had already moved to the new GSM network that was rolled out from 1994 onwards.
Interception of telephone conversations by the police usually requires a court order (warrant). Without such a warrant, the police is not allowed to tap a phone line and the information obtained from the intercepted conversation can not be used as evidence in a court case.
In December 1994, after a series of incidents (known as the IRT-case), the Dutch parliament ordered a public hearing about the investigation methods used by the IRT of the Dutch Police [4]. The result was a public hearing that became known as the Van Traa Commission. The full text of the final Van Traa Report has been published online by Buro Jansen & Janssen [5].

The image on the right shows part of the Van Traa Commission at work on 23 October 1995 in The Hague (Netherlands). The second person from the left is chairman Maarten Van Traa [9].
The Van Traa Commission at work on 23 October 1995. ANP Historic Archive [9].

During the hearings it became publicly known that the police sometimes used 'special techniques' as an aid to their investigation. As it was sometimes unclear whether such techniques were allowed, they were kept secret. In some of the hearings, the existence of Kolibrie was revealed and confirmed by the interrogated detectives and, hence, it became known to criminals [6]. By the time of the hearings however, ATF-3 had already been largely replaced by the new GSM network.
Bringing Kolibrie back to live
As Crypto Museum wants to be a 'living museum', we would like to be able to demonstrate the operation of the Kolibrie. However, as the old underlying analogue NMT-900 network no longer exists, it will be very difficult to let this device perform the task it was designed for.
Furthermore, the 900 MHz band is nowadays (2014) used for a variety of other services, including various digital GSM networks and other TDM-based digital networks. This means that there will probably be no useful analogue signal today for the Kolibrie to lock-on to.

The image on the right shows the Kolibrie being powered up for the first time on our workbench. After the initial startup message, the unit asks for the Identification Plug to be inserted. Once the plug is inserted, the serial number is shown and the key is prompted to be removed again.
Powering our Kolibrie for the first time

Please note that it is vital to use the matching identification plug that has the same serial number as the Kolibrie itself. Without this plug, the unit can not be used. Collectors that have a Kolibrie without this plug, should read the section about the identification plug above.

In order to test the MT and BS receivers, we've used two RF signal generators; one running at 895 MHz (MT) and the other one at 940 MHz (BS). This causes the RRSI and both LEDs to come on shortly after scanning is started with the squelch (SQL) set to maximum. The latter is necessary in order to prevent locking onto spurious digital signals (such as GSM) as illustrated below.

As the band of the former base stations (935-960 MHz) is filled with fixed and multiplexed signals, we had to raise the level of our test signal significantly, in order to allow the Kolibrie to pick it up. Fortunately, the frequency segment for the mobile stations (890-915 MHz), the so-called uplink, was quiet enough for our test. The two analogue modulated signals were enough for our initial test and the Kolibrie immediately locked on to the 895 MHz test signal.

The image above shows the frequency spectrum in which Kolibrie operates. The frequencies used for our test are indicated with vertical dashed lines. The yellow block at the left shows the position of the local oscillator (VCO) that appeared on the spectrum analyzer when Kolibrie was in use. The LO signal can be detected at quite some distance from the device.

As we currently have no means of simulating the digital AFSK-based negotiation data, the upper line of the Kolibrie's display remains filled with dashes. If we would be able to simulate the handshake data between MT and BS, this line would show the caller ID and the dialled number.
Powering our Kolibrie for the first time Connecting the necessary cables at the rear Kolibrie Version 1.21 Insert Identification Plug ID Plug: NL127 Remove Identification Plug RSSI indicator and display Two RF generators simulating MT and BS

The NMT mobile phone network was a Scandinavian development and was used in the countries listed below, making these countries possible candidates for using a Kolibrie. Whenever known, the year in which the network was closed is given in brackets.
  • Asia
  • Bosnia
  • Bulgaria
  • Croatia
  • Czech Republic
  • Denmark
  • Estinia (2000)
  • Finland (2002)
  • Hungary
  • Iceland (2010)
  • Latvia
  • Lithuania
  • Netherlands (1997)
  • Norway (2004)
  • Poland
  • Romania
  • Russia (2008)
  • Serbia
  • Slovakia
  • Slovenia
  • Sweden (2007)
  • Switzerland
  • Turkey
  • Ukraine
We should like to thank Marcel Rohrs of The Netherlands for bringing the existence of the Kolibrie scanner to our attention [8]. In the early 2000s he was one of the first people to obtain a Kolibrie from a public government sale. When visiting Crypto Museum in March 2011, he was the first to demonstrate the unit to us. We then knew we had to find this clever high-tech tool.
ATF   Autotelefoon (carphone)
Name of the analogue Dutch mobile phone network. Starting with ATF-1 in 1980 (150 MHz), followed by ATF-2 in 1985 (450 MHz). The last analogue network was ATF-3 (900 MHz), based on the NMT-900 standard. ATF-3 was closed down in 1997.

GSM   Global System for Mobile communication
Digital mobile phone network. Also known as 2nd generation mobile phone (2G).

IRT   Interregionaal Recherche Team
Special investigation units of the Dutch Police, known as Inter-regional Investigation Teams, that existed in the early 1990s. A series of public hearings, known as the Van Traa Commission, revealed in 1996, that the IRT often used unofficial (and sometimes illegal) methods during their investigations, which eventually led to new laws on criminal investigation.

NMT   Nordic Mobile Telephone
Analogue cellular mobile phone network developed in Scandinavia in the mid-1980s. NMT-450 was the first network to be developed in the 450 MHz band. It was also the basis for the Dutch ATF-2 network. It was followed by the NMT-900 network, operating at 900 MHz. The latter was called ATF-3 in The Netherlands.

PVD   Politie Verbindings-Dienst
Dutch Police Signals Service. Responsible for communication and reladed equipment within the Dutch Police Force. Also the developers of the Kolibrie receiver.

  1. Wikipedia, Mobiele Telefoon
    History of the mobile telephony in The Netherlands (Dutch).

  2. Wikipedia, Nordic Mobile Telephone
    Good description of the NMT network standard.

  3. Maxim, Dallas Semiconductor, DS2401 Silicon Serial Number
    Datasheet of unique ID chip in TO92 case.

  4. Wikipedia, Parlementaire enquêtecommissie opsprongsmethoden
    Dutch public hearing and investigation of criminal investigation methods. Als known as the Van Traa Commission (Dutch).

  5. Buro Jansen & Janssen, Van Traa Rapport
    The full report of the public hearing, known as the Van Traa Commission. Nearly 5500 pages in Dutch. With full online search facility.

  6. Van Traa Report, Hearing number 21. Mr. A.M. Mosterd
    One of the documents of the Van Traa Report, revealing the existence of the Kolibrie intercept receiver. Hearing number 21, 14 September 1995. Dutch.

  7. Motorola Inc. MCMC68HC705C8 Technical Data
    Datasheet. Rev. 4, May 2002.

  8. Marcel Rohrs, Owner of a surplus Kolibrie
    Crypto Museum, March 2011.

  9. ANP Historisch Archief Community, Commissie Van Traa in de Eerste Kamer
    The Hague, 25 October 1995. Reproduced under the Creative Commons Licence.

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