The Certified Audio Recorders - The Field  Model                    Go to Home page   

     The Field Model has the following features:

  1. The recorder has an internal Knowles microphone as well as a 3.5 mm socket for an external electret microphone.

  2. The Recorder has an excellent audio quality in the range of 40 Hz to 4KHz with a dynamic range of > 70 dBs. Conversations can be heard up to 30 meters away in quiet conditions.

  3. A slider switch activates the recording. This slider switch is mounted inside the recorder housing. Once the recorder has been activated and the slider closed the recorder cannot be deactivated by mistake. The recorder also supports external activation via the 2.5 mm external socket. The recording will be automatically restarted in the event of a power interruption if the slider is in the on position on power up.

  4. During a recording the operator is able to listen to the audio being recorded. If the recording is running off batteries this will reduce the battery life of the recorder. The 2.5 mm socket is shared between a mono audio out and the external on off switch.

  5. The certified audio information and the certificates are stored on an industry standard Multi Media Card (MMC) or Secure Digital (SD) Card.

  6. There is a trade off between bandwidth (the amount of space needed to store the recordings) and quality. We have chosen to go for a high quality which results in a high bandwidth.

    An hour of recording takes up 16Mbytes of space. The audio recording duration is a function of the size of the MMC or S/D card. A 128 M-Byte MMC holds over eight hours of recording. A 1.0 G-Byte SD card holds 64 hours of recording.

  7. The certified audio recording can be copied to a Personal Computer via the USB 1.1 port. The audio can also can be read using a standard MMC/SD reader if desired. The recorder cannot delete a file on the MMC. If order to delete all recordings on the MMC or SD card the memory cards must be plugged into a recorder and cleared by a USB transferred command from the software running on the PC.

  8. At least twenty-four hours of continuous recording are possible with two (fresh) AA cells.

  9. A Smart Card chip is used for the cryptographic functionality, both for rapid operation and to guarantee the security of the secret keys.

  10. The audio can also be encrypted to ensure that only the intended party access the recording from the recorder. The recorder cannot decrypt the recording. Only authorised parties in possession of the correct USB control tokens can decrypt the audio files. Please see the section on Windows 2000 and XP based Control Systems.

  11. The recorder has an on-board playback mode. The user can select audio files (tracks) and fast forward and reverse within the audio file. However there is no visual display of the track number or position within the recording. Playback is only allowed if authorised by the system controller and the audio file has not been encrypted.

  12. It is possible to measure the battery voltage using the USB interface.

  13. There is an external 6V DC external power socket. The user is advised to fit the internal AA batteries even when running from the external power supply. In the event of an interruption to the external power supply the internal AA batteries will act as a hot stand by for the recorder. This will result in one continuous recording even in the event of power interruptions. There is no charge drawn from the batteries when the recording is running from the external power supply.

  14. The gain of the audio circuit is controlled in a digital manner. The user can change the gain settings using the USB port. The gain settings on the internal and external paths are independent.

  15. It is possible to manually alter the audio gain setting of the by entering a special set up mode.

Physical Dimensions and Photographs

The current physical dimensions of the box are 125mm deep x 62mm wide x 24mm high. The quoted dimensions when viewed from the side of the box with the USB connector.

The front view:

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The following external interfaces appear on the front face of the device from right to left:

  1. DC power connector.

  2. Optional On / Off Slider Switch

  3. External Microphone Socket

  4. Internal Microphone

  5. Socket for external control input and mono-audio output.

  6. USB Connector

Rear View with Slide Open showing the second On / Off slider switch with two other special mode control buttons on either side:

Here is a slide side of the device showing the battery compartment:

 

CE Approval

This device has been successfully tested according to the following standards:

  1. Radiated Emissions tests done according to CISPR22 Class B (Commercial and Light Industrial) from 30MHz to 1 GHz. A copy of the test result is available here.

  2. Radiated Susceptibility tests done according to IEC 61000-4-3 from 80 MHz to 1 GHz at a level of 3V/m (80% 1kHz AM). The device continued to function during the test. No susceptible impairment of the recording made during the test was noted.

ESD (Electro Static Discharge) IEC 61000-4-2 is still is needed for full qualification. This will be done as soon (this was unavailable when I did the tests).

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