The invention relates to a circuit arrangement for the electrical isolation of signal lines, with an input (IN) for applying an input signal, an output (OUT) for releasing an output signal, and an initial branch (1) with an opto-coupler (OK) for optically coupling the input (TN) to the output (OUT), such that the input (IN) and the output (OUT) are connected in electrically isolated fashion by a second branch (2) with a capacitor (C1).