Abstract: A bus signal detector for a signal transmitted via a bus (12) has an edge detector (14) which supplies a signal (S.sub.F1) indicating the occurrence of a signal edge (F1) when the voltage on the bus (12) suddenly changes by at least a predetermined relative threshold (.DELTA.U.sub.s) in relation to a reference voltage (V.sub.ref) continuously adapted to the quiescent voltage of the bus (.sub.12). An evaluating circuit following the edge detector (14) uses the signal (S.sub.F1) supplied by the edge detector (14) to produce an output signal indicating a bus signal.