Subminiature covert tape recorder
The JBR, or Junior Body Recorder,
was a subminiature body wearable
developed by Nagra-Kudelski
in Cheseaux-sur-Lausanne (Switzerland)
in the mid-1980s as the successor to the Nagra SN.
The device can record two independent audio channels for up to 2 hours
and was initially developed for the
FBI and two
other US Government agencies. It was intended for
surveillance and wiretaps.
The existence of the JBR was kept secret for many years.
The JBR was about half the size
of its 1970 predecessor, the Nagra SN.
It measures only 110 x 64 x 21 mm and weights less than 200 g, including
and the tape.
It is a recording-only device, which means that
it has no playback facilities and no erease head.
As there is no erease head, the device is barely detectable by the sensors
of the era. In addition, the uncommon bias frequency of 32 kHz was used;
the same frequency that is commonly used in digital watches. Any further
emissions were reduced/eliminated by the solid aluminium case.
During the 1970s, 80s and 90s, a covert tape recorder was arguably the most
important element in an electronic surveillance operation. Incorrect operation
could easily jeopardize the operation. Contrary to
other surveillance recorders,
such as the Nagra-SN,
the JBR is constructed in such a way
that it can not be manipulated accidently by the agent. Once the
tape is loaded, the
remote start/stop switch is the only control available,
allowing a maximum recording time of 2 hours.
The JBR was introduced in 1984 and stayed in production for several years.
In total, 1118 units were built, mainly for US, Canadian and British Government
agencies, for a unit price well over $4000.
In 1986, the maching PS-1 playback unit
was introduced, of which 657 units were built .
In recent years, only a few devices have become available to collectors.
The JBR and the PS-1 were the last electromechnical devices from
Nagra, before digital recording became mainstream.
In 2007, the Nagra JBR was succeeded by the highly secret
Nagra CBR (Covert Body Recorder).
The image below shows a top view of the Nagra JBR. Compared to the
earlier Nagra SN,
there are no controls on the device whatsoever.
This was done to avoid operator-error. After installing the
loading a tape and connecting the peripherals (microphones
and remote control), the device is ready for use.
All the operator can do, is turn the device ON via the
As a result, there is no capstan and/or pinchroller, making the JBR
a virtually maintenance-free device.
The JBR has a takeup reel, which is driven by a motor and a gear,
and a supply reel that provides sufficient friction.
When loading a cassette,
the tape should be guided via the tension
arm at the bottom right, past the recording head and finally along the
black tape roller at the top right. The latter contains a built-in
that is used by the motor control system to compensate for
variations in speed, without the need for a flightwheel, a
capstan and a pinch roller.
At the front of the recorder are four
high-quality precision sockets
to which the peripherals are connected. The two rightmost 3-pin sockets
are for connection of the two covert microphones.
The 2nd socket from
the left is for the remote control unit
that is used to turn recording ON or OFF.
The leftmost socket is for connection of external device
for confidence playback testing.
Please note that on some devices, the leftmost socket (line in)
may have been modified for use in combination with an external power
supply. This was used in situations where the JBR had to be active
for more than 10 hours, e.g. on an unmanned wire-tap or a
Special high-precision connectors
are used for the peripherals.
Once inserted, the connectors are secured
by means of a tiny locking bolt
that can be tightened with a finger or fingernail. The image on the right
shows a JBR with both microphones and the remote control
The connectors have been constructed in such a way, that the cables
are nicely aligned with the body of the JBR, so that the entire device
can be hidden in, say, the pocket of a coat, or a special
holster under the clothing of the operator, whilst the cables are
carefully guided to their target.
At the bottom side of the recorder are three small LEDs, as shown in the
image on the right. The upper one (which is ON here) shows that the unit is
running and that battery life is sufficient for recording a full 2 hour tape.
Check that this LED is ON at the start of a new recording.
The lower LED indicates 'Audio Max'. It lights up when the audio signal on one
of the microphone input channels is within 3dB of the maximum allowed
level (equal to 30mV at the input). As a test, tapping the microphones
at the start of a recording should cause the lower LED to flash.
The middle LED is the 'Speed OK' indicator. It shows that the speed servo
circuit is locked at the correct speed and that the tape is transported
correctly. After switching the unit ON (i.e. when starting a recording),
a few seconds should be allowed for the speed to stabilize.
As the JBR is a record-only device, a separate unit is needed for playing
back a recording. Initially this was done on a specially adapted Nagra SN,
as a gap-fill solution, but eventually the
PS-1 playback system was introduced.
The PS-1 is a high-quality playback unit with a built-in Time Base Corrector
(TBS) that was especially designed for
the Nagra JBR cassettes. Like the JBR, it is fully maintenance free and has
no capstan or pinch roller.
➤ More information
The Nagra JBR was the successor to the Nagra SN
which, when it was introduced in 1970,
was the smallest professional tape recorder in the world.
The Nagra SN was the favorite recorder in the intelligence and
law enforcement community for many years and even made it to the moon.
Nevertheless, it could easily be detected with a so-called recorder
detector and was rather heavy, which is why eventually the Nagra
JBR was developed.
➤ More information
The Nagra JBR (and the PS-1 playback system) were the last electromechanical
covert recording systems made by Nagra before digital recording took over
and made them obsolete.
In 2007, Nagra introduced the CBR, or Covert Body Recorder, that was
smaller than a pack of cigarettes and did not have any moving parts.
Furthermore, the recordings contained a digital signature to avoid
tampering with the evidence.
➤ More information
The JBR can record audio onto a 3.81 mm wide chromium dioxide tape that was
contained in a proprietary Nagra cassette.
There are three recording channels:
two independent 1.2 mm audio channels plus a 0.4 mm control track
at the centre. The latter is used for a 5,461 Hz reference signal that allows
the separate PS-1 playback system
to correct for speed variations later.
The tape runs at a constant speed of 2.38 cm/s (15/16 ips) ± 2%
and there is no capstan.
Depending on the thickness of the tape, the recording time is 90 minutes
(12µ) or even 2 hours (9µ). The device is powered by
three N-size cells that provide up to 10 hours of recording time.
In order to increase the dynamic range of the recording, the JBR uses a
built-in compressor with a 2:1 ratio. When playing back the recording on
a PS-1 playback system,
the PS-1 will automatically compensate for this with its built-in
audio expander that can be adjusted for the best results.
Although the design of the Nagra JBR is very different from that of the
Nagra SNST, the tape format is close enough to allow
JBR-tapes to be played back on a Nagra SNST. This would only be used as
a last resort, as the SNSN does not have a control track and, hence,
no speed stabilizer.
This solution was also used in the two years after the introduction of the
JBR, before the PS-1 playback system became available in 1986.
Luckily, the tape width and the tape speed of the JBR are identical
to that of the SNST, as is the position of the two audio tracks on the tape.
But there are also differences between the two.
The dynamic sound compression range on
the SNST is 70dB, compared to 80dB on the JBR recorder.
Furthermore, the JBR uses chromium dioxide
tapes, whereas the SNST uses iron oxide1 tapes.
The image above  shows a special JBR cassette holder mounted to the right
side of a Nagra SNST. The JBR cassette is mounted onto the holder in the usual
manner, with an extended tape path that runs via the tape guides,
the playback head and the capstan of the SNST.
It is currently not known how the JBR cassette adapter is driven and how
tape tension is maintained. Any further information
would be greatly appreciated.
Image kindly supplied by Søren Ragsdale .
Iron oxide (Fe2O3)
was the initial substrate used on audio tapes in the 1960s
and 70s. It is also known as ferric-oxide and ferro oxide.
I was later superseded by chromium dioxide (CrO2).
Neither the JBR recorder, nor the PS-1 playback system are capable of
earasing the tape. This means that for every new recording, you need
either a fresh new (blank) tape, or a previously used one that has been
erased with a bulk-eraser.
During the 1970s, 80s and 90s, tape recorders were frequently used by
law enforcement and intelligence agencies to gather evidence about a suspect.
They were often worn by undercover operatives and had to be hidden carefully
so that they would not be detected by the subject.
Conventional tape (cassette) recorders had the disadvantage that they
contained an erase head. When making a new recording, the erase head
wipes any previous recording first. However, the frequency used for this,
typically in the 150-300 kHz range, is rather strong and can be detected.
When criminals discovered this, they started using small detection devices
like the TRD-800
shown in the image on the right. It consists of a small battery
powered unit that can be hidden on the body, and has a cable with an antenna
at the end, which was usually attached to the wrist.
When the criminal suspected a hidden tape recorder on one of his guests,
he would shake the persons hand and inconspicuously move the hand with the
detector on the wrist over the persons body, especially over the areas where
a tape recorder was likely to be hidden. If the device picked up the frequency
of the erase head, it would discretely alarm the operator by starting to
Some of the devices were so sensitive that they could even sense the
bias signal of the recording head, which usually had the same frequency
but was much weaker. This allowed criminals to even detect recorders
with a disabled erase head.
The JBR did not have an erase head, so that it could not be detected by
the majority of the recorder detectors of the era. In addition, the bias
signal of the recording head was given the uncommon frequency of 32.768 kHz,
the same frequency as is used by digital watches, which was known not
to trigger the detector's alarm.
And to avoid even the smallest risk of detection, the JBR was housed in
a very tight aluminium enclosure, that shielded off any remaining unwanted
radio signals that could be picked up by a sensitive device.
This technique of shielding off unwanted emanations is also known as TEMPEST.
➤ More about the TRD-800 detector
In the mid-1980s, the FBI
had a growing need for a sub-miniature undetectable
tape recorder for critical surveillance tasks and wiretapping.
As no portable tape recorder
at the time met the tough specifications of the FBI - not even
the Nagra SN - the FBI teamed up
with Nagra Magnetics Inc., the US subsidary of the Swiss
to see if a proprietary unit could be developed .
It was decided that a new tape recorder would be designed, which would
be smaller that any existing professional surveillance recorder and that
would be virtually undetectable.
On behalf of the FBI, Jim B. Reames1 helped the design
team . It has been rumoured that his initials (JBR) were used as the name for
the device, but this has neither been confirmed nor denied by NAGRA.
In order to keep the new device as small as possible, it was decided to
leave the play-back facilities out. Furthermore, the JBR had no erease head
and used an uncommon frequency (32 kHz) for the recording bias signal.
This frequency is also used by digital watches and would not be noticed
by the recorder detectors that were commonly used at the time.
As the JBR is housed in a solid aluminium enclosure, the remaining
unwanted emission is kept to a minimum. For playback, the separate
was developed, which became available a few years later.
As the US Government did not want the JBR to become available to other
users, or even publicly known, it was decided to keep the device secret.
It was not mentioned in any brochure and it was
never shown and demonstrated at technology shows. All marketing for the unit
had to be done via word of mouth.
In September 1990, Nagra wanted to advertise the JBR in the Law and Order
magazine, but received a letter from an undisclosed US Government agency
that prevented them from doing so. If they did, the letter stated,
NAGRA would lose all US Government contracts .
Besides the FBI, there were two other US Government agencies who had access
to the newly developed JBR technology (one of which was probably the CIA).
Later, other US Government
Agencies were allowed to use the JBR too, and even some Canadian and British
agencies were given access to the new technology.
Between 1958 and 1990, James B Reames was a Supervisory Special Agent
at the FBI, where he was involved in research and development of special
tape recorders and playback systems. In 1993, after his retirement from
the FBI, he founded his own company, JBR Technology Inc. that specializes
in professional forensic services and products .
The following accessories were either supplied with the JBR,
or were available separately:
Special highly sensitive miniature microphones
with a wide dynamic range were used,
in order to guarantee a good quality recording regardless the distance
between the microphone and the subject. These microphones could easily
be concealed in or under the operator's clothing.
The microphone shown here is encapsuled in a piece of shrink tube, to protect
it agains dust and damage. This way it can easily be taped to the body or
The external remote control unit is the only operator control that is
available. It is connected to the 4-pin socket at the side of the recorder.
Without this remote control unit, the Nagra JBR can not be used.
The remote control unit is identical to the external START/STOP control
of the Nagra SN, albeit with a different connector at the other end of
For the JBR, Nagra developed its own proprietary tape cassette format.
The thickness and the width of the tape is identical to that of the
Nagra SN, but the supply reel and the takeup reel
are integrated into a single unit.
When loading the cassette, the user has to guide de tape manually
over the tape rollers along the recording head. A metal clip
is provided to prevent the tape from running off the reel when it is
outside the recorder.
No Swiss high-precision device, such as a Nagra recorder, should come
without a Swiss-made precision tool, like this small screwdriver.
It can be used for opening the recorder in case it needs servicing,
or when the internal fuse has to be replaced. It can also be used for
repairing the connectors if necessary.
The nagra JBR was supplied in a small black box, along with the
standard peripherals, batteries and the operator's manual.
Inside the storage case was the usual black polyether foam, with
cut-outs for the various parts.
After all these years, it is normal for such foam to desintegrate,
so whe have replaced it in the storage box shown here.
The Nagra JBR is powered by three 1.5V N-size batteries
(approx. half the length of AAA-size batteries) that are
inside the recorder. The battery compartment
can be accessed via a rectangular cut-out at the top panel.
The batteries should be inserted as indicated on the body of the recorder,
with the (+) contacts towards the left. The battery compartment is not
closed with a panel.
The JBR was supplied with an instruction manual at A6 size,
which was normally stored behind the white flap in the top lid
of the storage case.
The manual measures 147 x 12 mm, which is about DIN A6 landscape format,
and is printed in black and white . It has two fold-outs: one at the
front and one at the back on which all functions and controls are
➤ Download the manual
From a mechanical point of view, the recorder is extremely simple.
The few moving parts
that are present, are mounted onto a frame
that is milled out of a solid block of aluminium.
This frame is mounted inside an light metal alloy shell that acts
as one half of the case (the bottom).
Another light metal alloy shell is used as the removable cover.
When using the recorder in an operational context, the cover
should be locked in place by means of a sliding lock at either side.
The frame has a spring suspension, so that it can move freely (within a
small margin) inside the case shell, and is held in place by a
single spring-loaded bolt.
Removing this bolt gives access to the interior
and allows the frame to be turned away as shown in the image on the right.
This results in
two halves that are connected together
via a bundle of thin wires (see below).
The first thing to notice when looking at the interior, is the absense
of any moving part, except for the motor.
The left half
(i.e. the rear of the mechanical frame) contains the motor,
the sensors and two PCBs with the control circuits.
The right half
(i.e. the bottom shell of the case) contains the power circuit
and the audio circuits, of which
two identical ones are mounted side-by-side.
The only mechanical parts of the JBR are located
under the thin dark plastic panel
on top of the frame. They can be accessed by
removing three tiny screws from the plastic panel.
The image above shows the various parts as
seen from the top.
At the centre is a large white wheel that is driven via a red belt
by a small electric motor below. The white wheel is part of the gear
that drives the takeup reel at the right. The belt allows the gear to
slip in case the tape is blocked.
At the left is the supply reel that has a friction break.
It consists of a hardened metal disc with a
v-cut at the outer rim, through which a thin steel wire runs. This steel
wire acts as the break.
When there is no tension on the tape, the break
is on and the supply reel is stopped. Any
tension on the tape however, is
sensed by the tape-tension arm at the bottom right, which will then
gradually release the break via the tape-tension transfer arm. The entire
tension system is clearly visible
in the image on the right. It can be adjusted with an
eccentic screw at the top left.
Although the motor speed is crystal controlled and an
optical encoder is used
to measure and correct the speed continuously, the absence of a flightwheel
will cause unwanted short-term variations in speed that are known as
wow and flutter.
This problem is solved by adding a control track with a 5.461 kHz signal
in between the two audio channels. This signal is later used by the
Time Base Corrector (TBC) inside the
PS-1 playback system to calculate any corrections.
Devices like the Nagra SN, the JBR and the PS-1 would have been the
ideal gadgets for the spy movies of the 1970s. At the time however, these
machines were highly secret and were probably unknown to the public
and to film makers. As far as we know the JBR/PS-1 have never been features
in a blockbuster movie. Until now that is.
Movie: The Coldest City (2017)
The Nagra JBR and the accompanying PS-1 playback station, are featured
in the forthcoming Thriller The Coldest Day, in which an
undercover MI6 agent is sent to Berlin during the Cold War to investigate
the murder of a fellow agent and recover a missing list of double agents.
The movie was shot in Berlin (Germany) and Budapest (Hungary) in 2015
and is expected to be released on 11 August 2017 (USA).
Crypto Museum supplied the Nagra gadgets for this movie.
➤ The Coldest City on IMDB
- Dimensions: (L x W x H): 110.2 x 62.6 x 20.8 mm (with cover)
- Power: 2.7 - 4V DC (nominal 4.5V)
- Battery 'OK' indicator threshold: 3.4V
- Batteries: 3 x AAA-size (ASA 'N')
- Current: 40 mA typical (at end of tape: 50 mA)
- Inputs: 2 x microphone, 80 kOhm, 60 mV RMS max.
- Audio indicator threshold: 30 mV RMS (-3 dB)
- Microphone sensitivity: 10 mV/Pa (1 Pa = 10 µBar)
- Frequency response: 170 Hz - 4.5 kHz ± 3dB
- Totl harmonic distortion: < 3%
- Compression ratio: 2:1 (in dB)
- Compressor range: 80 dB
- S/N ratio: > 51 dB (unexpanded, ASA A weighted)
- Tape speed: 2.38 cm/s (15/15 ips) ± 2%
- Wow and flutter: 2.5% peak-to-peak typical NAB weighted (DIN 45507)
- Starting time: < 4 seconds
- Recorder with cover: 143 g
- Cassette (2 hours): 22 g
- Batteries (3 pieces): 29 g
- Microphones (2 pieces with cables): 30 g
- Remote control (with cable): 18 g
- Total weight: 242 g
- Full Disclosure, The War on Privacy Hits You in the Pocket Book
Full Disclosure Newspaper, Libertyville, Illinois (USA). 1991
Retrieved July 2014.
- Nagra, Production overview and quantities
Internal Nagra document. Date unknown, but probably 2000.
- Nagra, JBR subminiature recorder
Product brochure, 2 pages. June 1092.
- Nagra Kudelski SA, Nagra JBR Instruction Manual
Code no.: 20.26002.151. May 1986.
- JBR Technology Inc. When every word counts
Website. Last updated 2008. Retrieved July 2014.
- Søren Ragsdale, Image of JBR cassette playback via Nagra SN
Image via Flickr. Personal correspondence, July 2014.
- James B. Reames, Personal Correspondence
Retrieved July 2014.
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© Crypto Museum. Created: Friday 04 July 2014. Last changed: Friday, 08 January 2021 - 16:20 CET.