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Unitel 225
Portable surveillance kit

Unitel 225 is a portable intelligence kit, consisting of a body wearable covert transmitter and a VHF surveillance receiver with cassette recorder in a Halliburton briefcase, introduced around 1994 by Audio Intelligence Devices (AID) in Fort Lauderdale (Florida, USA). It is basically a spin-off from the stand-alone RX-1000 digital surveillance receiver. The kit was used by the law-enforce­ment and intelligence community (mainly in the US) to gather evidence in covert operations.

The system operated in the VHF-H radio band, using frequencies between 150 and 174 MHz. 1 The receiver can be propgrammed freely within this range in 2.5 kHz steps, while the covert body transmitter operates on a fixed crystal-determined spot frequency. As the kit was used to gather evidence in criminal investigations, the conversation could be recorded with the built-in Marantz PMD201 audio cassette recorder.

The image on the right shows the complete kit, which is housed in a Halliburton briefcase, of which the lid contains the concealed antenna.
  

As a countermeasure against eavesdropping, the body transmitter has a built-in scram­bler and the receiver has a compatible descrambler. As the scrambler is based on inversion of the audio spectrum — which is easily circumvented — it only offers basic protection against an occasional (unintended) eavesdropper, but not against a professional interceptor. In the US, law enforcement and intelligce personnel from CIA, FBI and Police, were trained on this equipment at the National Intelligence Academy (NIA) — at the time AID's in-house training centre in Fort Lauderdale.

  1. 135-150 MHz by special request.

Open briefcase
Unitel 225 in briefcase
With antenna and microphone connected
Noise cancelling electret microphone with short cable
Knowles electret microphone with long flexible cable
Marantz PMD201 cassette recorder
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Open briefcase
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Unitel 225 in briefcase
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With antenna and microphone connected
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Noise cancelling electret microphone with short cable
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Knowles electret microphone with long flexible cable
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Marantz PMD201 cassette recorder
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Features
Below is an overview of the complete surveillance kit as supplied in the briefcase. At the front left are the power circuits and the built-in digital receiver, which is basically the separately available RX-1000 in a different enclosure. The case lid holds the antenna for the receiver. It must be connected to the base unit after opening the lid. For evidence gathering, the conversation could be recorded on the Marantz PMD201 cassette recorder which is mounted on top of the base unit.


All accessories and spare parts are stowed in the compartment at the right, including the body-wearable transmitter and a selection of concealable microphones and antennas. Although the receiver can be programmed to any frequency in the 150-174 MHz band (in 2.5 kHz steps), the body transmitter works on a single predetermined spot frequency. The unit can be powered by internal rechargeable batteries, by an external 12V DC source, such as the battery of a car, or directly from the 115 or 230V AC mains. This allows quick deployment of the system.


Parts
Halliburton briefcase
VHF Surveillance receiver
Marantz PMD201/221 cassette recorder
TX-916 Body Transmitter
TX
Accessories and spares
Operating instructions
Briefcase
The complete intelligence kit is housed in a Halliburton-style briefcase with plastic shells. The receiver and the recorder are permanently moun­ted inside the bottom case shell, while the antenna is integrated with the case lid.

To the right of the receiver is storage space for the body transmitter and the accessories.
  

Receiver
The receiver is integrated with the bottom half of the briefcase. It is basically a digitally controlled RX-1000 VHF/FM surveillance receiver that was also available from AID as a separate device.

The receiver is powered by an internal rechar­geable NiCd battery, or directly from the mains by means of the buil-in power supply unit (PSU).

 RX-1000 surveillance receiver

  

Recorder
The received conversation could be recorded onto a magnetic tape compact cassette by means of the Marantz PMD201 cassette recorder [E] that is mounted on top of the receiver.

The device is connected directly to the receiver and can be configured in such a way that it automatically starts recording as soon as the signal from the body transmitter is picked up.

 Operating instructions
 Service documentation

  

Transmitter
The Unitel 225 intelligence kit was supplied with a body worn transmitter model TX-715, TX-716 or TX-916. It was intended for concealment under the agent's clothing in covert operations.

The kit shown here came with the TX-916 trans­mitter, which has a built-in scrambler and an output power of 1W. It transmits at a predeter­mined spot frequency in the 150-174 MHz frequency band, controlled by a quartz crystal.

 More information

  

Accessories
The Unitel 225 came with a range of accessories and spares, such as a body transmitter, covert microphones, wire antenna, spare batteries, spare fuses, mains power cable and a 12V DC cable for powering the receiver from the cigarette lighter socket in a car.

The accessories are stowed in the right half of the bottom case shell, which allows quick deploiment during a covert operation.
  

Operating instructions
The kit was supplied with two A5-size booklets with operating instructions for the complete kit and for the body transmitter respectively. The manuals are available for download below.

The operating instructions are sometimes stowed inside the case lid as shown in the image on the right. The list also contains the primary antenna and short form instructions.

 Unitel 225 manual
 TX-916 body transmitter manual

  

Briefcase with Unitel 225
Open briefcase
Open briefcase
Operating instructions and embedded antenna in case lid
Antenna connection
Power section
Digital receiver
Body transmitter and accessories
Receiver access panel
Marantz PMD201 cassette recorder
Accessories
TX-916 body transmitter with accessoriries
With antenna and microphone connected
Noise cancelling electret microphone with short cable
Knowles electret microphone with long flexible cable
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×
B
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Briefcase with Unitel 225
B
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Open briefcase
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Open briefcase
B
4 / 16
Operating instructions and embedded antenna in case lid
B
5 / 16
Antenna connection
B
6 / 16
Power section
B
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Digital receiver
B
8 / 16
Body transmitter and accessories
B
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Receiver access panel
B
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Marantz PMD201 cassette recorder
B
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11 / 16
B
12 / 16
Accessories
B
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TX-916 body transmitter with accessoriries
B
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With antenna and microphone connected
B
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Noise cancelling electret microphone with short cable
B
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Knowles electret microphone with long flexible cable

Interior
The entire intelligence kit — basically a portable Listening Post (LP) — is mounted inside the bot­tom half of a Halliburton briefcase with outer dimensions 460 × 350 × 165 mm. The electronics are covered by a grey aluminium panel. The Marantz cassette recorder is mounted at the top.

The receiver can be accessed by first removing the Marantz cassette recoder and then opening the access panel below it. It is mainly used for accessing the descrambler plug-in board. It reveals the receiver printed circuit board (PCB) – shown in the image on the right – which is nearly identical to that of the AID RX-1000 receiver.

The differences with the RX-1000 are that the mains transformer and the synthesizer are not mounted on the PCB but elsewhere in the case. This was done to reduce the overall height of the reveiver and align the controls with the panel.
  

To access the mains PSU, the synthesizer and the internal rechargeable batteries, the entire panel must be removed from the briefcase. This is done by removing six bolts from the edges of the panel. After this, the panel can be raised, whilst the accessory compartment remains in place.

At the centre of the raised panel is the receiver, which is housed in a metal enclosure. To the left of this enclosure are the additional parts, such as the mains transformer, the synthesizer and the speaker, as shown in the image on the right. When accessing this part of the device, ensure that the power cord is disconnected from the mains, as some parts carry a lethal voltage.

The rechargeable batteries are located at the bottom of the lower case shell. They consist of two series-connected grey 6V gel batteries with an in-line fuse in the middle for extra safety.
  

The batteries are held in place by pre-shaped foam compartments, with another layer of foam on top. Based on date codes on the various internal parts and a written date on the rechargeable batteries, it seems likely that the device shown here was manufactured around October 1997.

WARNING — Before opening the device, ensure that it is disconnected from the mains. Some internal components carry a live voltage that is potential lethal. Always remove the mains cord completely before opening the cover.
Receiver access panel
Digital receiver under control panel lid
RF section and 1st mixer
Descrambler
Wiring to synthesizer
Bottom section
Battery compartment
Two rechargeable 6V gel batteries
Internal wiring
PSU, backup battery and synthesizer
Backup battery
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C
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Receiver access panel
C
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Digital receiver under control panel lid
C
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RF section and 1st mixer
C
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Descrambler
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Wiring to synthesizer
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Bottom section
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Battery compartment
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Two rechargeable 6V gel batteries
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Internal wiring
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PSU, backup battery and synthesizer
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Backup battery

Restoration
With a device of this age — it was more than 25 years old when we received it — it is always wise to check it thoroughly before connecting it to the mains. As the device had previously been used in the US it was configured for 115V AC. Before connecting it to the mains network in continental Europe, it first had to be set to 230V. Luckily this is simple as the selector is at the control panel.

After turning it on, it worked immediately with no serious problems. It was noted that the internal batteries did not hold their charge, but this was anticipated. It is unlikely that batteries of this age (1997) will still hold any charge at all. Although gel batteries generally do not leak, we decided to remove them. They can always be replace by a fresh set later.

After powering up the TX-916 body transmitter, it's signal was picked up instantly by the built-in receiver. The quality of the sound is still very good. The only remaining problem at the moment is the Marantz cassette deck. Although it is well-preserved, the three internal belts are completely worn-out and have to be replaced.

To be continued...

Problems
  • Cassette recorder doesn't run (belts worn out)
  • Compact cassette missing
  • Rechargeable batteries dead
  • Antenna cable foam missing
  • Mains cable for continental Europe missing
Solved
  • Exterior cleaned
  • Interior cleaned
  • Rechargeable batteries removed
  • Continental mains cable added
  • New C60 compact cassette added
Specifications
  • Device
    Surveillance kit
  • Purpose
    Evidence gathering and radio monitoring
  • Model
    Unitel 225
  • Catalog
    94567
  • Manufacturer
    Audio Intelligence Devices (AID)
  • Users
    CIA, FBI, Police, etc.
  • Year(s)
    1994-2000 (est.)
  • Band
    VHF-H
  • Frequency
    150-174 MHz
  • Spacing
    2.5 kHz
  • Modulation
    Narrow-band FM
  • Recorder
    Marantz PMD201 (or PMD221)
  • Transmitter
    TX-715, TX-716 or TX-916
  • Mains
    110-120 V/AC or 220-230V/AC 50/60Hz (switch selectable)
  • Battery
    Internal (see below)
  • External
    12V/DC (e.g. car battery)
  • Dimensions
    460 × 350 × 165 mm
  • Weight
    10 kg
Batteries
  • 2 × A 506 6.5S
    6V/6.5 Ah
    Sonnenschein A500
    07895465
Checklist
Documentation
  1. Unitel 225 - Operating Instructions
    Westinghouse, Audio Intelligence Devices, Inc.
    90035-17/0910811. Rev. 3, November 1996.

  2. TX-716 / TX-916 - Operating Instructions
    Westinghouse, Audio Intelligence Devices, Inc.
    90035-18/G109107. Rev. 2, January 1996.

  3. BXR-2202 - Operating Instructions
    Westinghouse, Audio Intelligence Devices, Inc.
    90031-17/G920707. Rev. 2, April 1996.

  4. The Use of Cigarette Lighter Receptacles as a Voltage Source...
    Westinghouse, Audio Intelligence Devices, Inc.
    90033-07/G920807. Rev. 1, June 1997.

  5. Model PMD201/PMD221 Owner's Manual
    Marantz. Undated.

  6. Marantz PMD201/221 Service Manual
    4822 725 50867. Undated.
Further information
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Crypto Museum. Created: Friday 19 January 2024. Last changed: Monday, 22 January 2024 - 16:11 CET.
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