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CIA FBI AID
The device measures 102 × 57 × 18 mm and weights 176 grams, batteries included.
It has rounded corners and could easily be hidden under the clothing. In
practice, the device was often worn in a special harness or taped to the body,
along with microphone and antenna.
Different antennas and microphones
were available on request.
Because the antenna is close to the body, the theoretical range of the
transmitter is reduced, which is why the TX-922 has an output power of 1W.
With fresh alkaline batteries, it can be used continuously for
at least 3 hours. 2
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Body transmitters are also known as a wire, and the person wearing it,
is said to be wired.
In covert operations, body transmitters were often preferred over
body-wearable (tape) recorders,
as they allow other officers to monitor and witness the
operation, while still being able to record the conversation. For
this reason, the TX-922 was commonly used in combination with a portable
listening post like the Unitel 225,
which consists of a receiver with a built-in tape recorder.
The device shown here was used for many years by the German Police, until
it was superceeded by newer devices.
It is similar to the TX-722, which has an output power of 250 mW. 3
It can be used with virtually any
general coverage surveillance receiver,
but was often used in combination with a matching AID
receiver, such as the analogue RX-905,
the digital RX-1000
or the Unitel 225 intelligence kit.
Due to its nature (VHF/FM) it can easily be detected by regualar
TSCM equipment.
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135-150 MHz by special request.
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More when Lithium batteries are used.
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The low-power TX-722 had a battery life of at least 24 hours.
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The image below shows the TX-922 with its case shell removed.
The actual transmitter
measures only 45 × 57 × 18 mm and uses two common
9V battery cells that are connected in parallel.
An antenna — usually a piece of wire — is connected to the mini BNC socket at
the left. The socket at the right is for connection of an electret microphone.
It accepts a screwable 2.5 mm mini-jack.
The device is enabled by setting the slide switch aside the antenna socket to the ON
position.
To prevent the batteries from falling out during an operation,
the case shell was usually secured by means of tape. In the same vein, the
power switch was often secured with a piece of tape so that it
could not be turned OFF accidentally by rubbing against it.
This is why the ID label of devices like this is often barely readable.
The device shown here was probably carried in a body harness.
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The device is housed in a metal enclosure that consists of two case halfs,
held together by means of two strong spring steel lips aside the battery
compartment. The actual transmitter is held inside the upper case part. Its
interior can be accessed by removing five recessed screws (two at either side,
and one at the top) and the nut around the microphone receptacle, as shown above.
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Once the screws and the nut are removed, the interior can be taken from
the case shell. This reveals the transmitter, as shown in the image on the right.
It consists of two parts: the actual transmitter (here shown at the top right) and
the battery holder with the two quartz crystals (at the bottom left),
interconnected by five wires.
Each crystal has its own adjustable coil so that it can be tuned accurately to the
specified frequency. The transmitter consists of a crystal oscillator,
an amplifier stage and a power amplifier (PA) that produces the desired 1W.
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In between the transmitter and the front panel is a small PCB that holds
a microphone amplifier with compressor/limiter. This is done to ensure that the
device picks up any sound in the room – soft or loud – and amplify it to the
desired level, so that it can be monitored, recorded and or transcribed
at the nearby listening post. Using a sound compressor improves the intelligibility.
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When we received the TX-922 featured here [1], it was cosmetically in good
condition, but unfortunately it wasn't working. This is probably the
reason why the device had been discarded.
A first test showed us that the device was drawing no current whatsoever.
After closely inspecting the interior, we discovered that the short wire
between the centre contact of the on/off switch and the circuit board was
broken. This rigid wire is clearly visible in the image on the right.
It was replaced by a slighty longer and more flexible one, so that it won't break
again.
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With the new wire in place, the device was tested again and this time it worked
as expected. Both channels produce a strong and clear RF signal, with proper
suppression of the harmonics. It complies with the original test report that was
made to get official FCC approval [A].
Further tests revealed that the original microphone wasn't working properly.
Although it worked initially, tapping it or rubbing it against the clothing muted
it instantly. 1 As it is housed in a sealed plastic enclosure, there is nothing
we can do to fix it. It was therefore replaced by a similar one from
Knowles.
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The muting effect might also be caused by the transmitter's internal sound
compressor/limiter, but it didn't occur with a replacement microphone from the
TX-916 in our collection.
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Device Body-wearable covert transmitter Purpose Evidence gathering and room overhearing Model TX-922 Catalog ? Manufacturer Audio Intelligence Devices (AID) Distributor Technos International Year 1994 (est.) Country USA Users CIA, FBI, Police, German Police Band VHF-H Frequency 150-174 MHz Method Crystal 1 Channels 2 Waveform Narrow-band FM Output 1W Antenna Wire (mini-BNC) Power 9V Battery 2 × 9V alkaline (type 1604) Duration 3 hours Microphone Knowles electret with long wire
Noice cancelling electret microphone (short wire) Dimensions 102 × 57 × 18 mm Weight 84 g (176 g with batteries)
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The device shown here operates at spot frequencies of 168.360 and 168.240 MHz.
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- Anonymous donor, TX-922 body transmitter - THANKS!
Crypto Museum, December 2024.
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© Crypto Museum. Created: Saturday 28 December 2024. Last changed: Sunday, 29 December 2024 - 09:09 CET.
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