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Nagra
Long duration audio logging recorder
- this page is a stub
- wanted item
TRVR, short for Two-track Rack-mountable Voice Recorder, is an open-reel
audio tape recorder for continuous recording or playback,
introduced in 1979 by Nagra Kudelski
in Chesaux-sur-Lausanne (Switzerland).
By cascading two or more TRVR machines, 24/7 operation could be achieved.
Apart from telephone line and radio channel monitoring, the device was also
used for automated operation of radio stations (play-out), and for recording
air traffic conversations [2].
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The device was usually mounted in a standard 19" rack and was operated in
vertical position. Its tape drive mechanism is unique in that it does not
have a capstan and pinch-roller. The TRVR can record two audio channels (stereo)
simultaneously and has a third channel on which IRIG B timecode
is recorded. This way, fragments can be retrieved quickly and unambiguously.
The device is fully remote-controllable and can be cascaded, so that a
backup machine is started automatically when the tape-end is reached or
an alarm is raised, allowing 24/7 operation.
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The TRVR has separate recording and playback heads, so that each recording
can be monitored in real-time. Whenever the level of the playback signal is
reduced – for example due to a degraded or worn-out tape, or dirty heads, an
alarm will be raised. The two VU meters are not only used to check the level
of the recorded signal, but can be used for a
variety of other purposes as well.
The TRVR was used by several intelligence services
for monitoring telephone lines under investigation.
It is known that it was used by the British intelligence service MI5
and by the Victoria Police Force in Melbourne (Australia) [3].
The device was also used as a play-out system by radio stations
– such as Radio Monte Carlo – for its 24 hour broadcast service.
Nagra introduced the TRVR in 1979 and it remained in production until 1987 [2].
In total, 435 units were made [1].
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- Rack-mountable (19")
- AC and DC operation (control signals)
- Excellent frequency response and S/N ratio at lowest speed
- Long recording time (> 12 hours)
- Continous recording (self-checking)
- Advanced tape transport mechanism
- Auto-start on input signal (VOX)
- Remote control with indication
- Keyboard lock (safety measure)
- Bi-directional servo-controlled tape drive
- End-of-tape sensing
- Built-in time compressor/expander
- Built-in timecode generator (IRIG B)
- Cascaded operation with standby recorders
- Advanced maintenance facilities
- No capstan and pinch-roller
- Continuously variable speed control
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- Telephone line voice logging
- Dialogue recording for air traffic controllers
- Radio broadcast play-out systems
- Telephone and radio monitoring and intercept
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The short 2:30 minute video clip on the right shows the Nagra TRVR in operation.
No commentary.
Source: scaudio390 on YouTube [4].
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This video clip shows how the tape is loaded
Source: Specializes in Imported Bandage Heads on YouTube.
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Device Rack-mountable voice recorder Purpose Telephone line monitoring Manufacturer Nagra Model TRVR Years 1979-1987 Channels 2 (stereo) + timecode Timecode IRIG B Tape width 6.25 mm (1/4") Thickness 18µm — 50 µm Diameter 17.8 cm (max) Speed 2.38, 4.75, 9.5, 19 cm/s Accuracy ± 0.1% Recording 12:30 hrs (18µm on 17.8 cm reel at 2.38 cm/s) Startup < 0.1 sec Input 77.5mV (timecode 25mV to 10V) Power 20-30V DC Consumption 800 mA Quantity 435 Temperature -20°C to +70°C Dimensions 480 × 320 × 310 mm Weight 16 kg
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- Input and output signal level (dB)
- Timecode input and output level (dB)
- Difference between recorded and playback level (dB)
- HF bias level (for maintenance)
- Remaining tape quantity (%)
- Configured and actual DC start level (V)
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Tape speed
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in/s
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Frequency Response 1
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W&F
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S/N
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2.38 cm/s
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15/16
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170-5,000 Hz
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< 0.15%
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50 dB
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4.75 cm/s
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1 7/8
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170-10,000 Hz
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< 0.09%
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55 dB
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9.5 cm/s
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3 3/4
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170-15,000 Hz
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< 0.07%
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58 dB
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19 cm/s
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7 1/2
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170-17,000 Hz
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< 0.07%
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58 dB
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The lower end can be extended to 30 Hz.
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© Crypto Museum. Created: Tuesday 21 November 2023. Last changed: Tuesday, 21 November 2023 - 14:57 CET.
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