Abstract: A network protection method and apparatus are disclosed for alerting an operator when a terminal device is disconnected from the network. A network controller adapter is connected to a network control computer. The network controller periodically stops normal data communication and scans some or all of the network ports to ascertain the present and absent status of a terminal device at each port. Status is detected by passing a current through a port and measuring the feedback voltage. If the status changes between scans, an operator is alerted by sounding an alarm at the network control computer or by other steps such as dialing a telephone number and transmitting a stored message or by transmitting an alarm message over the network to one of the terminal devices such as a personal computer.

Abstract: A TFT LCD display has a PEL matrix in which the drain lines of the different TFTs are supplied with different drain voltages to achieve a preset number of gray scales. The different drain voltages are set during factory calibration through use of a test PEL having substantially the same characteristics as the PELs viewable by a user. The characteristics of the test PEL are first measured, the values of drain voltages for achieving the different gray scales are mathematically derived from the measurements, and such values are stored in the display system. The specific manner in which calibration is done is by measuring output voltages of a photodiode located next to the test PEL as a function of different drain voltage inputs and constructing a unique transmissivity versus drain voltage for the subject display. Calibration is accomplished by a factory tester or by a built-in calibration system.

Abstract: A TFT LCD display has a PEL matrix in which the drain lines of the different TFTs are supplied with different drain voltages to achieve a preset number of gray scales. The different drain voltages are set during calibration through use of a test PEL having substantially the same characteristics as the PELs viewable by a user. The characteristics of the test PEL are first measured and the values of drain voltages for achieving the different gray scales are mathematically derived from the measurements. The specific manner in which this is done is by placing a photodiode next to the test PEL and measuring the photodiode outputs corresponding to different drain voltage inputs to construct a unique transmissivity versus drain voltage for the subject monitor.