To avoid the breakdown of several stub lines in case of a short-circuit, line separators may be inserted. The line separator is used where several stub lines are connected to the FDnet/C-NET at one point, if no other device is given between the T-tap. For retrofitting of existing, collective systems to addressable Sinteso/Cerberus PRO fire detection systems. The line separator is an electronic switch, integrated into the FDnet/C-NET. It separates the negative conductor in case of a short-circuit, so that the short-circuit-free side can continue to operate. The line separator has 2x2 connectors for the detector line. Yellow LED for the status indication signals the short-circuit separation.