| 摘要 |
The invention relates to a method for monitoring keyboards in digital line-fed terminals for key pressure. Keys arranged in columns and rows are monitored by applying a test potential row by row and testing for existing potential column by column. The object of the invention consists in carrying out the monitoring in the idle state with a minimum of energy. This object is achieved by the device sending out the test potential being switched inactive in the idle state, all rows being connected to 0-potential via a switching section controllable by a flip flop and all columns additionally being connected to the inputs of a common NAND gate for setting up the potential test and, on key actuation, the 0-potential of the corresponding row passing via the NAND gate to the flip flop, disconnects the 0-potential from all rows and switches on the device sending out the test potential. Thus, the active energy-consuming keyboard monitoring arrangement is only switched on during the keyboard operating time.
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