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Body wires BND AID
The TX-775 was typically used by a law enforcement or intelligence service
during covert operations, in which case it was commonly known as a
body-wire. The conversation could then be monitored and recorded
in a nearby listening post.
The device has nearly the same height and width as its successors, such as the
TX-916, but is somewhat thinner: 14 mm instead of 18 mm.
This makes it somewhat easier to conceal under the clothing. The thinner body
was possible due to the use of a proprietary battery, whereas
its successors uses standard COTS 9V batteries.
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The device shown here was used by a German intelligence service. It
transmits on 168.360 MHz, which is known as
BOS Channel 41. It is
assigned to the Bundesgrenzschutz (BGS), but as it is an
inter-services channel, it was also used by other agencies, including
the BND, BfV and MAD. It allowed
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The image below provides a quick overview of the features of the TX-775
transmitter. In the image, the lower case shell has been removed in order
to access the battery compartment. The battery itself has been removed.
There are two connections at the top: one mini-BNC-like socket for the
antenna, and a 2.5 mm jack socket for the microphone. The latter has a
fixating nut on its plug. Also at the top is a miniature ON/OFF slide switch.
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The interior can be accessed by removing five miniature screws –
two from either side and one from the top – and the nut of the microphone
socket. This allows the printed circuit board (PCB) to be
extracted from the enclosure.
This reveals the interior, as shown in the image below.
Inside the device is a single PCB with components on either side.
The design is a mixture of conventional miniature parts and
surface mount devices (SMD); something that might be expected
from a design of the late 1980s. The PCB is neatly fitted inside
a U-shaped frame that also holds the antenna and microphone sockets,
and the power switch. Two thin red and black flying wires connect the
battery cradle to the PCB. The battery cradle is designed to hold
a standard military non-chargeable battery of the era, type BT70192
or 5K69, neither of which is available today.
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When we received the TX-775 in March 2026, is was in excellent cosmetic condition,
but was untested since the original non-chargeable batteries were dead, and
replacement batteries were no longer available. Luckily it came with four empty
batteries, one of which had been emptied by a previous owner. We converted it
into a power cable adapter than can be connected to a PSU.
After connecting the antenna and the supplied microphone, it was
powered via the newly constructed adapter
and switched ON. It transmitted perfectly at the
frequency listed on the label (168.360 MHz), but didn't produce an audible signal.
After checking the microphone, it turned out that the cable was broken, close to
the jack plug. The cable was shortened by 2 cm and resoldered. The device now works
perfectly again.
The only problem that remains, is the issue with the battery. If we want
to be able to demonstrate the device without a cable to a nearby PSU, we
will have to create an alternative battery. For this, we have emptied one of
the other dead batteries. We will now look for alternative cells, such as
rechargeable flat-pack Li-ion cells.
To be continued...
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- Batteries dead
- New batteries (or replacements) no longer available
Microphone dead
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- Battery converted to power cable adapter
- Microphone cable repaired
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Device Body-wearable surveillance transmitter Purpose Covert overhearing of conversations Model TX-775 Manufacturer AID Distributor Technos International (USA) Year 1986 Country USA Frequency 150-174 MHz 1 Channels 1 2 Waveform Narrowband FM Oscillator Crystal-controlled Output 200 mW (est.) Microphone Electret (external) Antenna ¼λ flexible wire with mini-BNC-like connector 4 Approval FCC ID: BYK8SYTX775 (1986-11-25) 3 Power 7.2 - 9 V/DC Current 120 mA (@ 9V) Battery BT70192, 5K69 (military) Dimensions HWD: 104 × 52 × 14 mm Weight 60 g (104 g with battery pack) Price ?
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On special order: 130-150 MHz or 216-200 MHz.
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The device featured here, is programmed for 168.360 MHz, which is
known as BOS channel 41. It was used as an inter-services channel
by BND, MAD, BfV and other BOS services.
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This number does not appear in the FCC database. The number on
the label (BYK8SYTX775) is wrong and should probably be B348PTTX775,
approved on 25 November 1986.
The confusion likely stems from the fact that AID has two registration
prefixes: B34 for AID and BYK for AID Technical Systems Division.
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The antenna connector is similar but not identical to a mini-BNC.
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- Anonymous, TX-775 body transmitter - THANKS !
December 2025.
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© Crypto Museum. Created: Friday 04 September 2026. Last changed: Saturday, 05 September 2026 - 17:00 CET.
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