Abstract: The present invention discloses a proximity sensing system and an autonomous device, like a vacuum-cleaner, being provided with a pair of independent driven wheels (17, 18). The device contains for the proximity orientation and guiding a microprocessor system and a sonar system which includes at least an ultrasonic transmitter and an ultrasonic receiver. An additional mechanical touch sensor is also used in the form of a forward directed bumper (16) carrying the transmitter as well as receiving microphone units. The mechanical bumper actuates at least one touch sensor if the device makes contact with an obstacle in the course of the moving device. The transmitter is a stripe-shaped ultrasound transducer (10) which is positioned at the front of the device and transmits ultrasonic waves with a narrow vertical distribution within a wide sector in front of the device. The receiver includes a number of microphone units (12) provided with hollow pipes (12a, 12b) for the sound.