The TLE 4917 is an Integrated Hall-Effect Sensor designed specifically to meet the requirements of low-power devices. e.g. as an On/Off switch in Cellular Flip-Phones， with battery operating voltages of 2.4V ? 5.5V. Precise magnetic switching points and high temperature stability are achieved through the unique design of the internal circuit. An onboard clock scheme is used to reduce the average operating current of the IC. During the operate phase the IC compares the actual magnetic field detected with the internally compensated switching points. The output Q is switched at the end of each operating phase. During the Stand-by phase the output stage is latched and the current consumption of the device reduced to some μA. The IC switching behaviour is omnipolar， i.e. it can be switched on with either the North or South pole of a magnet. The PRG pin can be connected to VS which holds the output VQ at a High level for B=0mT; conversely the output VQ can be inverted by connecting the PRG pin to GND， which will hold the output VQ at a Low level for B=0mT. In this later case the presence of an adequate magnetic field will cause the output VQ to switch to a High level （ i.e. off state ）.