Importance

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Abstract

A battery-powered magnetic pen has an oscillator for generating a magnetic field at a contact frequency and a proximity frequency. The oscillator is connected to a resettable timer. The pen also includes a tip switch that is actuated in response to the pen being brought into engagement with an object and disengaged from the object. The tip switch is connected to a pulse generator and to the oscillator. Each time the pen is brought into engagement with an object, the pulse generator resets the timer to initiate the timing of a time out period. Assuming the oscillator is off, the first time the pen contacts an object, the resetting causes the oscillator to be turned on. So long as the oscillator is on, the opening and closing of the tip switch causes the oscillator to switch between the contact frequency and the proximity frequency. Should the timer reach the end of a predetermined time out period, the oscillator is shut off. Thus, if the tip switch is continuously actuated for the time out period, such as might occur due to improper storage of the pen, the oscillator is shut off to prevent the battery from becoming discharged.

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First Claim