The Behringer Radar in detail:

Radar by Behringer is an unusual Eurorack controller that converts touch into control voltages. The module is a replica of the Mutable Instruments Ears, which is based on the Contact microphone by Tom Whitwell. A very sensitive contact microphone converts scratching, tapping, rubbing and other movements into a control voltage and a Gate . The control voltage is actually a mini-envelope whose attack and decay times are selectable in fast, medium and slow by switch. The contact microphone is so sensitive that, with the appropriate gain level, it can also process ambient noise or the slight tremor of turned-up speakers as control voltages. Optionally, an audio signal such as a synthesizer, a guitar or a normal microphone can be used instead of the contact microphone. The audio output prepares the signal from the contact microphone or external sound source to Eurorack level so that it can be used in patches.