A data input device including plural keys that are arranged over at least two lines. A unidirectional position detector is associated with each line of keys and each unidirectional position detector includes a first input connection, a second input connection, and an output connection. The output connections of the unidirectional position detectors are connected at different locations to a first ohmic resistor. In addition, the first input connections are connected to a first terminal of the data input device and the second input connections are connected to a second terminal of the data input device.