Time Expansion Mode
This mode is used to enable computer analysis of bat calls as an aid to identifying species. Using time expansion a bat call is recorded and played back at a reduced speed. With the Tranquility II you have a choice of playback speed, either ten times slower ( ÷ 10) or 32 times slower ( ÷ 32).
The played back signal is recorded on a conventional tape recorder for subsequent computer analysis.
Use the ÷ 10 playback for computer work and ÷ 32 playback for human listening.
The Tranquility II recognises a bat call and automatically starts a recording and playback cycle at your selected speed. The length of the recorded time is 1280ms, that is 1.28 seconds of bat call.
As an example of time expanded bat calls consider the calls from a Noctule.
They tend to be split into three sections.
The first section is a signal of approx. 35kHz sweeping down to 25kHz in 10ms.
The second section is a silent gap of 5ms.
The third section is a signal of 25kHz sweeping down to 20kHz in 10ms.
The sounds of this signal is quite different to the ‘Click’ sounds from a heterodyne detector.

If ÷ 32 playback is selected the loudspeaker output will be a sweep of 1kHz to 780Hz in 320ms, followed by a silence for 160ms and finally a sweep from 780Hz to 625Hz for 320ms. The sound is quite spectacular and resembles a whale call ( that is a speeded up whale call ) and is slightly unnerving.

Heterodyne Mode
When used in this mode the Tranquility behaves as a conventional detector & is tuneable over the ultrasonic frequency range 12kHz to 120kHz. This range is suitable for all UK and European bat species.

When used as a heterodyne receiver the TIME switch must be set to a TUNE position. The tuned frequency is displayed on a large seven segment LED display. This display is very accurate due to the use of a crystal controlled time reference.

Heterodyne frequency is adjusted using a single turn potentiometer & the peak power frequency of calls can be quickly determined. Very useful for example in distinguishing between 45kHz and 55kHz Pipistrelles.

The Tranquility II has an inbuilt loudspeaker. Alternatively, a low impedance headphone may be used. Insertion of a headphone jack into the HD jack socket will disconnect the internal speaker. For stereo headphone both earpieces are energised.

The REC output jack socket is used for connection to a tape recorder.

Power requirement :- four AA size batteries. To change batteries remove the bottom cover.


  1. Time Expansion Mode :- Frequency range 10kHz to 200kHz.

  2. Record time 20ms, 40ms, 320ms, 1280ms at 200kHz bandwidth.

    Sample rate 409.6kHz.

    Playback rate ÷10 ( for PC analysis ), ÷32 ( for human ears ).

    Record/playback sequence automatic.
  3. Superheterodyne Mode :- Tuning range 12kHz to 120kHz. Bandwidth ±3kHz.
  4. Sensor type. Single wideband capacitive.
  5. Display. Three seven-segment digital 9mm LED.
  6. Output jack connections :- a) HD stereo headphone socket. b) REC tape recorder socket.
  7. Tuning control. Single turn potentiometer.
  8. Batteries :- x 4 AAcells. Battery life approx. 35 hours.
  9. Internal loudspeaker. Maximum audio output power 400mW.
  10. Control knobs. Collet types.
  11. Housing. Purpose built ABS 4mm thick.
  12. Approximate weight 500gm (with batteries). Size 95 x 154x 36mm.
  13. The detector is not water proof, and should be protected from rain. Any water on battery terminals will cause corrosion.
Guarantee : The Tranquility II is guaranteed for 1 year, provided the detector has not been physically damaged. There are no user replaceable parts other than four batteries which are replaced by removing the bottom cover.

Price : (U.K) £439.00 plus registered* post & packaging (£7.20) Total:£446.20

( * Royal Mail special delivery insurance to stated value.)

The above price is valid until 30th June 2001

[click the here to see larger image]
The Tranquility II is a second-generation bat detector/recorder. It is two detectors in one, a conventional heterodyne receiver, and a time expansion receiver. It uses a wideband sensor.
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