D500X Ultrasound Detector/Recorder Mk II

The D500X Mk II is as easy to use and provides the same features as the classic D500X, with the following exceptions: 

*It does not include an internal microphone. Instead it ships with an external microphone which is either directly connected to the microphone jack or through an extension cable. The microphone jack is an XLR type so no adapter cable is required.

*It is powered by 4 C type batteries which last roughly three times longer than the AA batteries used in the classic D500X.

*The jack for external power is a standard 2.5 mm DC power jack for easy connection.


The D500X is an ultrasound recording unit intended for long-term, unattended recording of bat calls. In contrast to time expansion bat detectors, the D500X records full-spectrum ultrasound in real time with virtually no gaps between recordings. The recorder is equipped with four slots for CF cards, which typically makes it possible to leave the unit in the field for more than a month. The triggering system allows the device to automatically start recording as a sound is detected.

The recording length can be selected in steps from 0.3 up to 20 seconds (or continuous in manual mode). In order not to fill the card too fast at locations with high activity, a minimum time between two recordings can be applied. The recorder is normally operated in a low-power mode with no pre-trigger (i.e. the recording starts as the sound exceeds the chosen threshold level), but both pre-and post-trigger functions are available in the standard (not low-power) mode. The D500X stores the bat calls in time stamped wav files.

The D500X comes in a rugged and weather-protected aluminium housing. A soft protection case with straps to hang the unit in e.g. a tree is included.

Various accessories are available, such as microphone extension cables (up to 100 m).

An instructional video by Bat Conservation and Management.


Type: Direct, high-speed recording
Microphone: Advanced electret, jack for external microphone
Frequency range: 15 kHz – 190 kHz (500 kHz sampling rate, high-pass filter enabled)
5 kHz - 190 kHz (500 kHz sampling rate, high-pass filter disabled)
Connections: External microphone, external DC supply
Timer: Four on/off periods per day
Batteries: 4 x C size, Alkaline or NiMH recommended
External DC supply: 5.5-8 V, typically ca. 200 mA (average, when recording), depends on CF card type and number of CF cards
Size: 165 x 170 x 53 mm, excl. connectors etc.
Weight: 1.3 kg incl. batteries and front panel cover

 Recording system

ADC resolution: 16 bits
Anti-aliasing filter: Yes, 8th order, 190 kHz cut-off frequency
Sampling rates: 44.1, 300, 500 kHz (optimized for 500 kHz)
Recording length: 0.3, 0.5, 1, 2, 3, 4, 5, 10, 20 sec or manual recording
Recording medium: CF card, 4 slots