Celltrack cellular interception system.

Celltrack cellular interception system.

Colebrand Company Brochures. — 1996.

Celltrack Cellular Interception System

The Celltrack device from Colebrand is a stand-alone device in a portable or stationary design for tracking mobile cellular radio telephones of the TACS/ETACS, AMPS/EAMPS NMT 4501/900 standards. Without intervention from the Celltrack computercan covertly find and track the desired users of mobile cellular radio telephones, track and record the digital channel of control codes and the sound of their voice channels, and solve a number of other problems that arise during reconnaissance operations. Celltrack has a modular design and can be used for tactical mobile operations or as a component of a stationary system for monitoring a large area.

The Celltrack system node includes a control computer (CC), radio modules (RM), control modules (CM), and an antenna splitter (AS).

All devices are connected via RS 485/RS 232 or Arcnet interfaces. The number of Celltrack radio modules is determined by the air traffic load, the number of channels and numbers to be intercepted. The tactical system has at least eight Celltrack radio modules. Seven of them are designed to track control channels, and one is for recording the voice signal. The external devices of the system include a modem, terminal, printer and tape recorder.

In cases where remote control or connection to other systems is required, a modem must be used. Celltrack is controlled via a computer terminal, with which the device can be fully controlled. Documentation and output to a printer of all interceptions and cell phone numbers within the receiver's coverage area are provided. Intercepted conversations can be recorded on a tape recorder or computer hard drive. There is an output to headphones for listening to conversations at the time of interception.

To the systemCelltrackincludes a control computer based on the 80486 processor equipped with a communications board. For mobile use, a laptop-type computer is used, for stationary installation — a desktop one. The computer's functions include distributing tasks between radio modules and storing switching information transmitted over the control channel on the disk. In addition, it stores the software of the radio modules and a database of numbers subject to interception. A database of all numbers registered in the receiver's coverage area and the time of registration can also be maintained. This information can be printed. When the control module determines a number subject to interception, the computer gives the radio module a command to intercept the conversation, and simultaneously turns on the tape recorder for recording. The system can operate autonomously or under the control of an operator.

The radio module is a frequency converter, the intermediate frequency of which is in the range of 800-960 MHz. It uses two-phase blocking circuits, mixers, detectors for simultaneous interception of direct control and speech channels, as well as the return speech channel. Tuning to the frequency is performed using a synthesizer.

The control module consists of an 80C552 processor running at 12 MHz with external RAM and EPROM. The EPROM contains a minimum amount of software sufficient to load the control software from the computer, which increases the security of the system and facilitates the installation of new software versions. Thus, the main part of the Celltrack software runs in 32 KB of RAM.

The module's system bus is built according to the I2C standard. Two parallel input/output PCF 8574 chips are connected to it, performing all switching functions, and the main cellular processors. Two such processors are required to decode the A and B streams of the forward control channel. Only one is used to track the transmission of data packets on the voice channel. The remaining digital control circuits, such as the phase-locking circuit of the receiver board and the cellular data recovery processors, are connected directly to the input/output contacts of the 80C522 processor.

The signal of the forward and reverse speech channels received from the receiver is amplified, switched and filtered in the frequency range of 300-3400 Hz, after which it is transmitted to the line output. The latter is equipped with a 3.5 mm jack and a 102-type jack. In addition, there is a pair of contacts for controlling the tape recorder, and a light indicator shows the operating modes. The unfiltered signal of the forward channel is transmitted to the decoding processors of cellular communication.

The Celltrack system is equipped with a serial interface RS 232/RS 485 or Arcnet. The Celltrack RS 485 chassis is used to connect modules via an RS 485/RS 232 converter. In racks consisting of several chassis, Arcnet is used to connect modules and control. In a system with one receiving module, RS 232 can be used.

Although high antenna sensitivity is generally not required to receive signals from ground stations, sometimes fixed systems require the use of directional antennas to separate signals from multiple stations sharing a single channel. Each antenna is connected to a splitter consisting of a filter, a high dynamic range amplifier, and a power divider.

In mobile interception systems, it is possible to use ordinary cellular antennas tuned to the middle of the forward and reverse ranges. It is possible to purchase camouflaged antennas for special applications.

The Celltrack system has a built-in direction-finding system that is controlled by a computer.

Immediately after turning on the Celltrack systemThe software required for operation is loaded into the receiving modules. One or more receiving modules scan the direct range and find the strongest signals. Having selected such signals, the receiving module begins to receive system messages. From these, such information as the traffic area ID, the number of paging channels, the number of access channels, and channel numbers is extracted.

By listening to the Supervising Audio Tone (SAT), the receiving module determines whether it is entirely within a single cell or on the boundary of two or more cells. The control computer determines the system configuration. Since the number of required Celltrack radio modules is determined by the air traffic load, the number of channels and numbers to be intercepted, configurations with different numbers of modules are possible.

The cell phone numbers to be intercepted can be loaded from the hard drive or entered from the keyboard. The size of the database storing the numbers depends on the application conditions and is determined by the user. If the number database is not defined, the system waits for instructions from the user. To bring Celltrack in working condition, the computer distributes paging and access channels between radio modules for listening. The selection of calls for listening is carried out in two ways: by the phone number of the device that receives/makes the call, and by the content of the conversation (manually).

Once a voice channel is selected automatically or manually, the system monitors the conversation as long as the phone is within the range of the interception system. Conversations are recorded on tape, and the numbers of all registered phones are stored by the computer. Both autonomous and user-controlled operation are possible.

To intercept conversations, the cell phone number must be entered into the number database. By this time, the access (reverse) and paging (direct) channels have already been distributed between the receiving modules for monitoring. When registering a number entered into the number database, the radio module informs the computer about it. When calling from a telephone or from a station, the receiving module transmits to the computer the number of the speech channel allocated for the conversation. The computer gives the radio module a command to intercept the specified forward and reverse speech channels. Then it connects the audio output to the tape recorder and turns it on for recording. The receiving modules intercept both the forward and reverse channels, taking into account the switching of the cell phone from one station to another. Thus, the entire conversation is recorded without interruptions for the entire time the cell phone is within the system's range.

To ensure maximum flexibility, the system has several operating modes. These are the scanning modes of the main, forward and reverse channels, detection of switching from one station to another, interception and decoding of data transmitted over the main control channel, interception of the forward and reverse control channels to detect specific telephone numbers.

There is an «intelligent exclusion» mode, which allows the operator to temporarily exclude a conversation of no interest to him while scanning the voice channels. As soon as the excluded channel becomes free, the system turns it back on. This mode is especially useful when the operator is waiting for the suspect to use his phone. Both the manual and automatic modes of the system are controlled from the computer terminal. In the manual mode, the following are possible:

• selection of any forward or reverse control channel with simultaneous display of all information transmitted on it;
• selection of any voice channel in simplex or duplex modes with or without tracking of switching from station to station;
• dynamic temporary exclusion of simplex or duplex channels to facilitate manually controlled searching;
• control of recording and playback of conversations on a tape recorder or digital recording system;
• viewing all cell phone numbers registered in the system coverage area.

In automatic mode, the following is possible:

• search for telephone conversations by the number of the calling or called cell phone;
• printing numbers of cell phones registered in the coverage area or leaving it;

Celltrack interception systems are supplied only to government law enforcement agencies. Each system is individually equipped in accordance with customer requirements and may include equipment not described here.

The supplier undertakes to provide installation and technical support of the system, as well as operator training. As the system development progresses, new versions will be presented to customers to maintain the proper technical level.

Technical specifications