DISPOSITIVO PER RIVELARE I GUASTI DI UTENTI DI ENERGIA ELETTRICA

To detect the failure of e.g. a lamp (2) supplied from a D.C. source (4) through a switch (3) controlled by a manually-operated member (5), a resistance (1) of much greater value than that of the lamp (2) is connected across the switch (3), and the voltage V1 across the resistance (1) is used for the required detection. If the lamp (2) goes open circuit, then when the switch (3) is non-conductive the voltage V1 is low instead of high, while if the lamp (2) is short circuited then when the switch (3) is conductive, due to the finite resistance of the switch (3), the voltage V1 is high instead of low. To ensure failure detection regardless of the condition of the control member (5), the switch (3) is caused cyclically to incurse momentarily into the opposite state from that dictated by the control member, so that either type of failure can always be detected; appropriate clock pulses are supplied from a generator (6). The equipment is particularly suited to detecting the failure of lights on a motor vehicle.