Convergence Technologies, Inc. (USA)  
   Bat detectors
   http://home.earthlink.net/~infocentr/faq.htm

Stag Electronics  
   Bat detectors, books and CDs of bat echolocation, downloads of bat sounds and bat music.
   http://www.batbox.com/

Ultra Sound Advice (UK)  
   Various ultrasound devices (air ultrasound, bat detectors, and data logger).
   http://www.ultrasoundadvice.co.uk/

Von Laar Media GmbH (Germany)  
   Bat detectors.
   http://www.vonlaarmedia.de/ids/eurobats.htm

Laar Bioacoustic  
   Sound analysis software, highspeed harddisk recording (ultrasound)for bats,dolphins,grasshoppers up to 500kHz sampling rate,multi-channel solutions,bat detectors,microphones,monitoring system
   http://www.vonlaarmedia.de/bvlint/default.htm

Bertrik's bat detector page  
   Information on building your own bat detector
   http://www.home.zonnet.nl/bertrik/bat/bat_indx.htm

Belfry Bat Detector  
   Hand built to order, an assembled unit that is portable, small, lightweight and is powered by a 9 volt battery.
   http://www.econvergence.net/batdet.htm

Pettersson Elektronik AB (Sweden)  
   Bat detectors
   http://www.batsound.com/