ELECTRONIC APPARATUS WITH AN ARRANGEMENT FOR FUNCTION KEY INTERROGATION

摘要

1. Electronic unit comprising a device for scanning function keys the actuation of which in each case causes a voltage drop characteristic of the actuated key across a current-fed resistance network, which voltage drop is scanned via an analogue/digital converter and evaluated via an evaluating device, characterized in that the resistance network (R 1, ... R n) is direct-current-connected to the voltage supply source (UB ) of the electronic unit and to the control input of a first switching device (T 1) in such a manner that the actuation of a function key (TA 1, ... TA n) releases a control current which activates the switching device (T 1) and effects the connection of the voltage supply source (UB ) to the supply input (UEIN ) of the electronic unit, and that a second switching device (T 2) is provided which, controlled by the analogue/digital converter (2) and the evaluation device (3), keeps the first switching device (T 1) in the activated state until the device function selected via the function key actuated has been executed.