DETECTOR, ISOLATOR, WARNING SYSTEM AND CONTROL METHOD

Providing a detector, an isolator, an alarm system, and a control method capable of operating with a capacitor having comparatively small capacitance. A detector (20) includes a short-circuit detection circuit (222), a relay (221), and a control unit (24). The relay (221) is disposed in an electric wire (31 or 32). The control unit (24) operates with the electric energy stored in a capacitive device. The control unit (24) is configured to repeat a steady-state operation for detecting an occurrence of a specified event, and further configured to open the contact device (2211) of the relay (221) in response to a detection of the occurrence of the short circuit by the short-circuit detection circuit (222). The relay (221) operates with the electric energy stored in the capacitive device to consume the electric energy while the short circuit occurs between the electric wires (31, 32). The control unit (24) is configured to, when the short-circuit detection circuit (222) detects the occurrence of the short circuit, open the contact device (2211) of the relay (221) prior to a first steady-state operation which is a first one of the steady-state operation after a detection of the occurrence of the short circuit.