Click for homepage
Video-over-radio system

RAICATS 1 is a video-over-radio (VOR) transmission system for simplex or half-duplex VHF/UHF radio, developed around 1996 by RACAL in Salisbury (UK), as part of the Cougar Radio portfolio. It was intended for covert use, and offers various baudrates, compression ratios and resolutions. Real-time video processing is achieved by means of Digital Signal Processing (DSP) technology.

The system consists of three functional blocks: an image transmitting unit (ITU), an image receiving unit (IRU) and a video camera. Two versions of the ITU are available: a desktop radio version (ITU-R) and a covert version (ITU-C).

The image on the right shows the ITU-C and IRU units, complete with the original NTSC video camera. At the lowest resolution of 128 by 128 pixels, it offers a maximum refresh rate of one image per second over a standard VHF or UHF radio link. At the highest resultion/quality the refresh rate slows down to 5 or even 8 seconds.
Complete RAICATS set

The portable ITU-C is housed in a die-cast aluminium enclosure, that is nearly identical to that of the Racal Cougar PRM-4515 portable radio. It was designed for use on EPM 2 channels, with a 16 kbps capacity, and was claimed to be highly error-resilient. It allows high-quality video images to be sent via a low-bandwidth radio channel to a base station, where they can be displayed on a PC [2]. For enhanced security, the device was often used in combination with an encryption system.

After Racal was taken over by Thomson (now: Thales) in 2000, the company used RAICATS as a technology demonstrator for future video systems [2]. In 2014, some remains of the RAICATS project ended up on the surplus marked, and devices were offered on auction sites like eBay.

  1. RAICATS = Racal Imagery Compression and Transmission System.
  2. EPM = Electronic Protection Methods [2].

Complete RAICATS set RAICATS IRU RAICATS ITU-C With battery pack Camera unit Front Rear
1 / 7
Complete RAICATS set
2 / 7
3 / 7
4 / 7
With battery pack
5 / 7
Camera unit
6 / 7
7 / 7

  1. Mutually exclusive. At the transmitting end, either an ITU-R or an ITU-C is used.

The diagram below shows how and where in the chain the units are used. At the left is the remote image transmitting station. It consists of a camera (CAM), an Image Transmitting Unit (ITU) and a transceiver (TX). At the right is the image receiving base station, which consists of a transceiver (RX), an Image Receiving Unit (IRU) and a MSDOS Personal Computer (PC) with a (colour) display.

Depending on the configuration and the (internal) settings, the base station can send commands to the remote station, to alter the latter's settings and to request one or more video images. Alternatively, the remote station can be configured to generate a constant stream of images. In addition each station can be given an address (1-31), so that it can be accessed individually.

The diagram below shows the controls and connections on the body of the MA-4807/B (ITU-C) transmission unit. It is housed in the same black die-cast aluminium enclosure as the Racal Cougar PRM-4515 encrypted VHF/UHF 1 radio, albeit with different controls and connections. It is powered by a 10V battery — the same one as for the PRM-4515 — that is attached at the bottom.

At the top is a recessed 7-pin socket for connection to the radio, plus a 4-pin socket — sticking out somewhat — for connection to the video camera, which also holds a trigger button. At the centre is the blue MODE-selector, which is shown here in the OFF-position. The function of the toggle switch just above the MODE-selector is currently unknown. There are two further blue selectors at the left side, for setting the Picture Attributes (PA) and Difference Treshold (DT).

MODE selector
  • OFF
  • Standby
    Waiting for over-the-air command
  • Active
    Transmitting images
  • Sleep
    Powered down, waiting for trigger (button)
Picture Attributes   PA
This setting defines the amount of detail of the image (resolution) as well as the compression ratio. There are 10 possible settings (0-9), of which the first five (0-4) have the lowest resolution (128 x 128 pixels), wehereas the last five (5-9) provide the highest resolution (320 x 240 pixels). A higher setting means more detail (i.e. less compression), at the cost of a lower refresh rate.

Difference Treshold   DT
The system has two ways of updating the picture: (1) ALL, which means that the whole image is transmitted, and (2) UPDATE, which means that only the areas which have changed from the previous image are transmitted. When in UPDATE mode, the DT-setting can be used to specify the Difference Treshold (DT), which is the amount of change before the image is transmitted.

  1. The PRM-4515 was available in a VHF-L, VHF-H and UHF variant.

RAICATS ITU-C with battery pack Controls and connections Additional controls Camera, front view Trigger button Pressing the trigger button on the camera
1 / 6
RAICATS ITU-C with battery pack
2 / 6
Controls and connections
3 / 6
Additional controls
4 / 6
Camera, front view
5 / 6
Trigger button
6 / 6
Pressing the trigger button on the camera

MA-4808A Image Receiving Unit
MA-4807B Image Transmitting Unit Covert NiCd battery for ITU-C Video camera module (NTSC) parallel connection between PC and IRU modem Cables for connecting the various units MSDOS PC software for IRU Short form instructions
IRU   MA-4808A
At the receiving end (i.e. the base station) the desktop unit – shown in the image on the right – is used for transferring the images from the radio (receiver) to a connected PC. Software for an MSDOS compatible computer is provided.

The device is effectively used as a
. The IRU is connected to the parallel port of an MSDOS PC, by means of the provided 25-way (DB25) ribbon cable.

ITU-C   MA-4807B
For field use – also known as covert use – the portable modem shown in the image on the right, was used at the transmitting side. It is housed in a die-cast aluminium enclosure, that is very similar to that of the Racal Cougar PRM-4515 portable radio.   

Battery   MA-4516
The portable ITU-C unit was powered by the same batteries as the Racal Cougar PRM-4515, which was attached at the bottom of the unit.

The battery is available in several sizes, with varying capacities. Most batteries were re-chargeable, but there were also versions that accepted (consumer market) AA-size dry cells.
With battery pack

The image on the right shows the video camera that was supplied with the set. It consists of a small rectangular aluminium enclosure with 4 mounting holes at the bottom, allowing it to be affixed to, say, a uniform or a soldier's webbing.

The camera is at the front. When it is not used, the lens can be protected by a plastic cap. At the sides are sockets for connection to the ITU and to an (optional) external trigger button.
Camera unit

Parallel cable
This short ribbon cable was provided for connecting the IRU modem to the parallel port of the PC – also known as the printer port or the Centronics port. At the time, printers were generally connected via a DB25 connector.   
Serial cable (DB25)

A shielded cable is used for connection of the camera to the ITU. The cable has a 4-pin male plug at one end, and a 4-pin female plug one at the other end.

The cable shown here is approx. 3 metres long, but for body-worn applications, a cable of one metre was usually sufficient.
Camera cable

A 3.5" floppy disc was supplied, with suitable software for a 66 MHz 486 Personal Computer (PC) with MSDOS 6.2 or later. It provides remote control of the ITU and its camera, and allows the received images to be displayed on the screen.

The latest known software version is 1.0, released on 5 February 1996. It is available for download as a ZIP-compressed image below.

 Download the software

Software on 3.5

The software (see above) was supplied with a 4-page A5 instruction sheet (folded A4), that describes how the units should be connected and configured. It also contains instructions for installing the software on an MSDOS computer.

The sheet also explains the function of the various DIP-switches inside the IRU receiver and inside the ITU-C transmitter.

 Download instruction card

Instruction card

The ITU-C is built to high production standards, similar to the Racal Cougar PRM-4515 handheld radio. The interior is accessible from both sides, by removing the front and rear panels, each of which is held in place by 9 recessed screws. After loosening them, the panels can be removed.

Inside the strong die-cast aluminium body, are two printed circuit boards (PCBs), one of which is the interface board. It connects the controls and sockets and holds the integrated video digitizer [b]. This board has components on both sides.

The other PCB is basically a daughter card of the interface board. It holds a second-generation TMS320 Digital Signal Processor (DSP) made by Texas Instruments (USA) [a]. The TMS320 was a popular component in the era, and was also used in other (voice) encryption equipment, like the Telsy CP7000 and the AT&T 4100 phones.
ITU-C interior

The DSP board is slotted into the large blue 54-pin female socket on the interface board, which is clearly visible in the image above. Apart from the TMS320 DSP, it also holds the RAM memory and two two EPROMs with the firmware. According to date codes on some parts, it was made in 1997.

The IRU (and also the ITU-R) is larger and more conventionally built. It is housed in a rectangular die-cast aluminium enclosure that is intended for desktop use. It's interior is accessible from the bottom, by removing eight recessed screws and taking off the bottom panel, as shown here.

Inside the case is just one PCB with components at both sides. It holds the radio interface, a DSP processor — the same one as used in the ITU — and a parallel interface to the PC. Looking at the PCB and the unpopulated space, it is evident that it was also used as the base of the ITU-R unit.
IRU interior

At the center of the board are two (colourful) DIP-switch arrays (marked SW1 and SW2) that are used for setting the internal configuration. They correspond to the two DIP-switch arrays inside the ITU, and should be set identical. The function of each switch is described in a table below.

Although the camera is arguably one of the most important parts of the kit, it is also the simplest part. It is housed in an off-the-shelf die-cast aluminium enclosure with four mounting holes.

At the top is a lid that is held in place by four large recessed screws. The interior can be accessed by removing these screws. Inside the box is not much more than a single-piece universal camera module that is mounted to the inside of the top lid, with its lens protruding it. It is sealed to make it water-resistant. Just three wires are needed for connecting the camera.
Camera unit - interior

The camera is wired directly to the 4-pin female socket mounted at one of the sides. At the other side is a 3-pin male socket that can be used to connect an (optional) external trigger switch, that is wired in parallel with the black trigger button that is present on the front of the camera body.

ITU-C interior ITU-C with the bottom side of the interface board visible Interface board - bottom side ITU-C interface board DIP-switches Wiring of the controls DSP board DSP board - top view
IRU interior IRU interior - top view DSP with firmware DIP-switches Opening the camera unit Camera unit - interior Camera - internal wiring Camera module
1 / 16
ITU-C interior
2 / 16
ITU-C with the bottom side of the interface board visible
3 / 16
Interface board - bottom side
4 / 16
ITU-C interface board
5 / 16
6 / 16
Wiring of the controls
7 / 16
DSP board
8 / 16
DSP board - top view
9 / 16
IRU interior
10 / 16
IRU interior - top view
11 / 16
DSP with firmware
12 / 16
13 / 16
Opening the camera unit
14 / 16
Camera unit - interior
15 / 16
Camera - internal wiring
16 / 16
Camera module

The recessed 7-pin female Clansman-style 105 socket at the top panel of the ITU-C, is used for connecting the device to a suitable VHF/UHF radio. It is wired as per Clansman standard, which is also supported by the later Bowman system. A Cougar/Clansman radio is wired as follows:

  1. Mic or Fixed Level Audio (FLA) or program input
  2. Mic return or Wideband programming
  3. Power in or out +10V (current out ≤ 100 mA)
  4. Audio/Data (AF out 400mW into 8Ω)
  5. Ground
  6. PTT or 4 kb/s data or key fill data
  7. Squelch or CTS
Below is the wiring of the 4-pin female camera socket on the top panel of the ITU-C, when looking into the socket. The 4-pin male socket on the body of the camera, is the mirrored version of the one shown here. The camera should be connected to the ITU by means of a 1:1 cable, of which at least one wire (4) must be shielded, as it carries the video signal.

  1. Trigger (switches to ground)
  2. Ground (0V)
  3. Power (+5V)
  4. Video 1Vpp NTSC
    Wiring of the camera socket on the IRU-C when looking into the socket
On the camera body are two sockets: a 4-pin male one for connection to the ITU (see above) and a 3-pin female one for connection of an external trigger button. When used, it must be connected to ground in order to cause a trigger. This means that the outer two pins should be shorted.

  1. Ground (0V)
  2. not connected
  3. Trigger (switches to ground)
    Wiring of the trigger socket on the camera, when looking into the socket
Inside the the transmitting and receiving units, are 16 DIP-switches that define the configuration. The switches are arranged as two sets of 8 DIP-switches each. The sets are marked SW1 and SW2 and are arranged as shown in the diagram below. At the left are the switches that are present on the top side of the PCB inside the IRU and the ITU-R. At the right are the switches that are present on the top side of the interface board inside the ITU-C. Both sides must be configured identically.

Switch 1
  1. Address bit 0
  2. Address bit 1
  3. Address bit 2
  4. Address bit 3
  5. Address bit 4
  6. Baudrate bit 0
    00 = 16 kb/s, 01 = 12 kb/s, 10 = 8 kb/s, 11 = 1200 baud
  7. Baudrate bit 1
  8. Picture mode
    OFF = all, ON = difference 1
  1. Should always be OFF to allow control from front panel swiches.

Switch 2
  1. Preamble time
    OFF = 100 ms, ON = 400 ms
  2. RX/TX delay bit 0
    00 = none, 01 = 200ms, 10 = 500ms, 11 = 2s
  3. RX/TX delay bit 1
  4. Squelch priority
    OFF = disable, ON = enable
  5. Link type
    OFF = half-duplex, ON = simplex
  6. Display colour
    OFF = colour, ON = Monochrome
  7. -
  8. -
Model Name Description
MA-4807/A ITU-R Desktop transmitting unit
MA-4807/B ITU-C Covert transmitting unit
MA-4808/A IRU Receiving unit
MA-4516W Battery Battery for ITU-C
611647 PSU Mains PSU for IRU
611950 Software 3.5" floppy with PC software
  • Radio
    16 kbps compatible radio
  • Connector
    US Style U238/U
  • Requirements
    66 MHz 486 PC with parallel port and MSDOS 6.2 or later
  • Interface
    Parallel (DB25)
  • Power
    10 — 15V DC (typically: 12V DC)
  • Dimensions
    255 x 155 x 45 mm
  • Weight
    1472 grams
  • Video input
    Composite video 1V-pp, NTSC, 75Ω
  • Compression
    Variable, 9 settings
  • Resolution
    128 x 128 or 320 x 240 pixels
  • Radio
    16 kbps compatible radio
  • Modem
    2400, 9600, 14400 or 19200 baud
  • Refresh rate
    1 second (128 x 128) or 5-8 seconds (320 x 240)
  • Connector
    US Style U238/U
  • Power
    10V DC battery (MA-4516 or equivalent)
  • Temperature
    0°C — +40°C (storage: -10°C — +55°C)
  • Dimensions
    159 x 75 x 30 mm (with battery: 236 x 75 x 30 mm)
  • Weight
    488 grams (without battery)
DT   Difference Treshold
In this context, its means the difference between the current picture and the previous one. It allows the system to limit the amount of data that is sent over the radio link, by only sending the differences.  More
EPM   Electronic Protection Methods
Expression - frequently used by Thales - for a radio channel that has been secured by means of electronic measures, like encryption (CRYPTO) and/or frequency hopping (FH). Also known as ECCM.
IRU   Image Receiving Unit
Desktop modem used at the receiving end of a RAICATS video link.
ITU-R   Image Transmitting Unit Radio
Desktop modem used at the transmitting end of a RAICATS video link.
ITU-C   Image Transmitting Unit Covert
Portable modem used at the transmitting end of a RAICATS video link in covert operations. ITU-C is an alternative to ITU-R.
NTSC   National Television Standards Committee
Analogue composite video standard that was (mainly) used in North America, from 1954 until 2010, when it was dropped in favour of digital systems. Incompatible with the PAL and SECAM standards that were used throughout Europe.  Wikipedia
PA   Picture Attributes
In this context, it is used to describe the properties of the video signal, in particular the resolution and the (lossy) compression ratio.  More
RAICATS   Racal Imagery Compression and Transmission System
System for sending video over a VHF or UHF radio channels with limited bandwidth.
VOR   Video over Radio
System for sending video images (stills or moving) over a radio link.
  1. RAICATS OPCARD, instruction sheet
    For radio systems with MA4807A/B & MA4808A. Software issue 1.0.
    IH145, issue 2. Racal, January 1997. 4 pages.

  2. RAICATS PC Software, version 1.0
    SP 3613/001-01. P611950. 5 February 1996.
  1. TMS320 Second-Generation Digital Signal Processors
    Texas Instruments, May 1987. Revised November 1990.

  2. SAA7191B Digital Multistandard Colour Decoder, Square Pixel (DMSD-SQP)
    Philips, August 1996.

  3. 74HC574, Octal D-type flip-flop
    Philips, NXP, Nexperia. Rev. 7 - 4 march 2016.
  1. Harald Hermanns, complete RAICATS kit - THANKS !
    Crypto Museum, January 2019.

  2. Thales Defence Communications, Panther EDR brochure
    Thales Defence Ltd., Bracknell (UK), January 2004. p. 8.

  3. Texas Instruments, TMS320 Second-Generation Digital Signal Processors
    May 1987. Revised November 1990. Retrieved May 2012.
Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
Crypto Museum. Created: Wednesday 09 January 2019. Last changed: Tuesday, 05 February 2019 - 12:19 CET.
Click for homepage