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Nagra JBR
Subminiature covert tape recorder

The JBR, or Junior Body Recorder, was a subminiature body wearable tape recorder, 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 covert operations, 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 the batteries 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.
Nagra JBR with cover

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 [2]. 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).
Storage case Nagra JBR with cover in place Nagra JBR with cover in place Nagra JBR with cover Nargra JBR without cover Nagra JBR with tape cassette, ready for use Running Nagra JBR compared to the size of a hand Nagra JBR ready for use - with 2 microphones and remote control

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 batteries, 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 remote control. As a result, there is no capstan and/or pinchroller, making the JBR a virtually maintenance-free device.

Top view of the Nagra JBR

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 optical encoder 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 voice-activated bug.

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 unit connected.
Nagra JBR with tape cassette, ready for use

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.
Three LEDs at the bottom - the power LED is on

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.
Top view of the Nagra JBR Nagra JBR tape cassette with tape-lock installed Nagra JBR with tape cassette, ready for use Close-up of the tape path - here showing the actual tape Side view, showing the connectors Close-up of the microphone connector Microphone connector in place Microphone connector locked

PS-1 playback system
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
Nagra PS-1 playback system for JBR covert recorder

Nagra SN
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
A Nagra JBR (right) aside a Nagra SN (left)

Nagra CBR
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
Nagra CBR with external batteries

Tape format
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.
Play back on Nagra SN
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 [6] 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 [6].
  1. 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).

Erasing tapes
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.
TRD-800 unit with dual mode antenna

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 vibrate.
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.
Antenna installed under the wrist band

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 Nagra Company, to see if a proprietary unit could be developed [1].

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 [7]. 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 PS-1 device 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 [1].

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.
  1. 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 [5].

The following accessories were either supplied with the JBR, or were available separately:
Miniature covert microphone External (wired) remote control switch (ON/OFF) Proprietary Nagra JBR tape cassette Swiss-made precision screwdriver Small black storage case The JBR needs three 1.5V N-size batteries Operator's manual

Covert microphone
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 clothing.
Covert microphone

Remote control
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 the cable.
Remote control (ON/OFF switch)

Tape Cassette
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 (shown here) is provided to prevent the tape from running off the reel when it is outside the recorder.
Nagra JBR tape cassette with tape-lock installed

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.
Swiss-made screwdriver

Storage case
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.
Nagra JBR with accessories in storage case

The Nagra JBR is powered by three 1.5V N-size batteries (approx. half the length of AAA-size batteries) that are installed 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.
Batteries installed

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 [4]. It has two fold-outs: one at the front and one at the back on which all functions and controls are summarised.

 Download the manual
Page 3 with both fold-outs

Bare microphone without the protective shrink tube Three N-size alkaline batteries Removing the tape lock Open end of the tape cassette Battery compartment Installing the batteries Batteries installed Nagra JBR ready for use - with 2 microphones and remote control
Instruction manual First text page the of instruction manual Page 2 and 3 with one fold-out Page 3 with both fold-outs

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).
Removing the mechanical section

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.
Nagra JBR gear and tape-tension mechanism

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.
Close-up of the spring-loaded bolt Spring-loaded bolt loosened Removing the spring-loaded bolt Removing the mechanical section Nagra JBR interior Nagra JBR interior - left half Nagra JBR interior - right half Close-upof the motor and the control circuits
Tape guide with built-in optical encoder Tape guide with optical pulse generator (seen from the interior) Early use of SMD ICs Close-up of the (two identical) audio circuits - using SMD technology Close-up of the LEDs Close-up of the spring-loaded battery compartment The audio boards mounted over the power board Close-up of the fuse
The gear of the Nagra JBR exposed Top view of the Nagra JBR with the mechanism exposed Nagra JBR gear and tape-tension mechanism Tape-tension in 'break' state Tape tension in 'release' state Tape tension in 'break' state Tape tension in 'release'state Close-up of the tape-tension adjustment

In popular culture
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

Technical specifications
  • 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
  1. Nagra, JBR subminiature recorder
    Product brochure, 2 pages. June 1092.

  2. Nagra Kudelski SA, Nagra JBR Instruction Manual
    Code no.: 20.26002.151. May 1986.

  1. Full Disclosure, The War on Privacy Hits You in the Pocket Book
    Full Disclosure Newspaper, Libertyville, Illinois (USA). 1991 Retrieved July 2014.

  2. Nagra, Production overview and quantities
    Internal Nagra document. Date unknown, but probably 2000.

  3. Nagra, JBR subminiature recorder
    Product brochure, 2 pages. June 1092.

  4. Nagra Kudelski SA, Nagra JBR Instruction Manual
    Code no.: 20.26002.151. May 1986.

  5. JBR Technology Inc. When every word counts
    Website. Last updated 2008. Retrieved July 2014.

  6. Søren Ragsdale, Image of JBR cassette playback via Nagra SN
    Image via Flickr. Personal correspondence, July 2014.

  7. James B. Reames, Personal Correspondence
    Retrieved July 2014.

Further information

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Crypto Museum. Created: Friday 04 July 2014. Last changed: Monday, 16 January 2017 - 22:12 CET.
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