SAFETY CIRCUIT ARRANGEMENT FOR THE FAIL-SAFE CONNECTION OR DISCONNECTION OF A HAZARDOUS INSTALLATION

摘要

A safety circuit arrangement for the fail-safe connection or disconnection of a hazardous installation (24) has a control device (12) which is designed to connect or interrupt, in failsafe fashion, a power supply path (20) to the installation (24). The safety circuit arrangement also has a signalling device (14) which is connected to the control device (12) via a number of lines (50, 52). The signalling device (14) has an actuator (40) which can change between a defined first state and a second state (40'). A pulse generator (42) in the signalling device (14) is designed to generate a defined pulsed signal (44) with a large number of signal pulses (46) on the lines (50, 52) when the actuator (40) is in the defined first state. According to one aspect of the invention, the signalling device (14) is connected to the control device (12) via a two-wire line (54) with a first and a second core (50, 52). A predominantly constant voltage is present between the two cores (50, 52) when the actuator (40) is in the second state. The pulse generator (42) is designed to bring about a voltage dip between the first core (50) and the second core (52) in order to generate the large number of signal pulses (46).