| 摘要 |
The method involves providing an operation voltage source with a first connection for the first operation voltage potential and a connection for a second operation voltage potential. First and second series circuits are provided with first and second resistors, first and second transistors and first and second current sources, respectively, and are connected to both connections of the operation voltage source. The connection of the first transistor with the first current source forms a connection for a signal line which has an ohmic load at the end turned away form the series circuit. A difference voltage (U3) is formed from the voltage (U32) at the connection between the first resistance and the first transistor and from the voltage (U31) at the connection between the second resistor and the second transistor. The magnitude of the difference voltage is formed. An output signal is changed according to the magnitude being below or above a predetermined threshold. The output signal indicates if the signal line is loaded with a load.
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