A handwriting capture system includes a portable electronic tablet that
capture pen strokes made on a standard pad of paper and transfer the
captured pen strokes to a digital image capture device such as a personal
data assistant or PDA using infrared communications circuitry. The
portable electronic tablet is battery powered, and the handwriting capture
system includes an infrared activated power switch to extend the useful
lifetime of the battery by power up the electronic tablet and infrared
communications circuitry only when the system is in use and otherwise by
powering off the electronic tablet and much of the communications
circuitry, in a manner that is entirely transparent to the user. An IR
activity detector remains powered up when the system generally is powered
off, and also furnishes power to at least the receiver section of the IR
transceiver. When infrared activity occurs, the receiver section indicates
that a signal has been received and the IR activity detector responds by
signaling a switched power supply to apply normal operating power to the
system.
