The GSW 2, and the very compact flush-mounted version GSW U2, are universal limit switches for wind monitoring. These switches, together with the wind sensor SW 2, can detect wind strengths of 2 - 8 (10-70 km/h). The wind sensor is powered by a potential-free safety voltage (10V DC PELV) from the GSW 2 or GSW U2, which means that no external power supply unit is needed.