Heterodyne bat detectors are great for beginners and for quick identification in the field by more experienced bat workers. They work by converting the ultrasonic bat call into a sound which is audible to the human ear. This process also enhances the tonal qualities of the bat call so that the wonderful differences in ticks, clicks, warbles and trills created by different species can be heard.
Heterodyne detectors, however, can only be tuned to one frequency at a time so it is possible to miss other bats as they are flying past. Models such as the Elekon Batscanner and the SSF Bat2 solve this problem by scanning all frequencies and automatically tuning the detector for you.
Recordings made from heterodyne detectors are useful for learning the sounds of different species, but they cannot be used with sound analysis software.