Närhetsbrytare, mål, system av sådana närhetsbrytare och mål samt metod för att bestämma ett måls närvaro medelst en närhetsbrytare

摘要

A proximity switch for detecting a target in proximity with the proximity switch as a wireless transmitter for transmitting a first pulsed signal having a first carrier frequency to the target. The proximity switch also includes a wireless receiver for receiving a second pulsed signal having a second carrier frequency different from the first carrier frequency from the target. The proximity switch has a controller for providing an output indicative of whether a predetermined correspondence is satisfied between the first and second pulsed signals.