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Recorder Detector

The TRD-800 was a small body worn recorder and bug detector developed and built by Research Electronics Inc. (REI) in Cookeville (Tennissee, USA) in 1989. It can be worn inconspicuously and allows RF devices, such as bugs, surveillance radios, and body worn recorders, to be detected, giving the operator a discrete visible or covert warning by means of LEDs or a built-in vibrator.

In the 1970s and 80s, tape recorders (and sometimes even wire recorders) were a common means for covertly recording conversations, for example during infiltrations, for espionage and in diplomatic traffic (e.g. embassy meetings).

Whilst recording a conversation, the recorder usually erases a previous recording by using a so-called erase head; an electromagnetic device that scrambles the particles on the magnetic tape. This is usually done by applying a high-frequency AC signal to the erase head. The TRD-800 was able to detect these frequencies.
TRD-800 unit with dual mode antenna

For this to work, the TRD-800 had to be very close to the recording device. In fact it had to be within the electro-magnetic field of the erase head. As the size of this field is usually no more than 10 to 20 cm, the antenna of the TRD-800 had to be moved over the body of the subject.

In order to do this covertly, the operator would place the antenna on his wrist, held in place with an elastic wrist band, with the cable running through his sleeve to the detector that was hidden, say, in his pocket. Whilst greeting the person, he could inconspicuously move his hand around the person under test. If a recording device was detected, the TRD-800 provided a feedback signal to the operator through the LEDs at the front panel or through the built-in vibrator. As it also contains a built-in RF detector, it is capable of detecting radio transmitters (bugs) as well.

During the cold war, tape recorders were a popular means for covertly recording a conversation, using miniature tape recorders such as the Protona Minifon, the Nagra SN or even small pocket memo recorders. Since the introduction of digital recorders (often integrated in mobile phones), tape recorders have gradually been phased out. As a result, the TRD-800 is no longer available from the manufacturer and the RF detection feature is covered by other TSCM products.

Storage case TRD-800 unit with dual mode antenna TRD-800 inside storage case Wrist band TRD-800 control panel TRD-800 and a compact cassette Placing the antenna under the wrist band Antenna installed under the wrist band

All controls of the TRD-800 are at the front panel as shown below. The unit is turned ON/OFF with the slide switch at the left, whilst the dual mode antenna is connected to the green 3-pin socket at the right. The two switches at the right are used to control the LEDs and the vibrator.

The red LED indicators are at the front panel. The leftmost one will light up when the battery voltage is getting too low and the battery needs to be charged. The middle LED lights up when a strong RF signal is picked up, for example from a radio bug. In areas with strong local radio stations, it might be necessary to press the RESET button after turning the unit on. The rightmost LED will light up when a tape recorder is detected. At the same time the vibrator gives a signal.

Considering the era in which the TRD-800 was developed, is extremely well built. The unit is housed in a fully metal enclosure that consist of two half case shells, held together by 8 small (hex) bolts. The detector is powered by a built-in 7.2V rechargeable NiCd battery pack.

Inside the case is a small L-shaped double-sided PCB with all components neatly mounted at the top side. At the bottom of the unit is the 7.2V NiCd battery pack that can be charged with the supplied mains adapter. The cut-out space in the PCB is used by a cubical vibrator, visible in the image on the right at the top centre.

The LEDs and the switches are all mounted onto a vertical sub-PCB that is soldered onto the main board. The 3-pin antenna socket is wired directly to the main PCB. This is done to avoid broken tracks from frequent plug movements.
Close-up of the interior. At the right is the (yellow) battery pack.

In order to protect the design of the TRD-800, the text has been removed from all of the ICs. Although the unit shown here is over 20 years old by now, it is still in excellent condition. Surprisingly, we were able to recharge the battery again after all these years, and use the TRD-800 for several hours. The battery is charged by connecting the supplied adapter at the rear.

Opened TRD-800 unit Interior before removing the foam Interior of the TRD-800 Close-up of the interior. At the right is the (yellow) battery pack. Top view of the interior of the TRD-800 Part of the interior and the front panel Close-up of the antenna Rear panel

  1. Research Electronics Inc., Unit Operating Instructions, Model TRD-800
    Original User Guide. Date unknown, but probably 1989.
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Crypto Museum. Created: Monday 20 May 2013. Last changed: Tuesday, 19 July 2016 - 07:45 CET.
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