Abstract: An earth fault circuit breaker (10) for use in a circuit including an AC power supply and a load (11), which circuit breaker comprises a current-to-voltage converter (12) having two transformers for monitoring the current before and after flowing through the load, a leakage current/voltage detector (13A) for processing the outputs (E1 & E2) of the transformers to produce a resultant voltage, a voltage comparator (16) for comparing the said resultant voltage with a predetermined reference voltage to determine if there is a difference between the two transformer outputs, which is caused by an earth fault appearing at the load, and a switching driver (14) for disconnecting the load from the power supply in response to such a difference between the two transformer outputs exceeding the predetermined reference voltage, wherein each transformer has first and second primary windings (P1 & P2) arranged to be connected to opposite sides of the load and the two transformers are arranged to provide outputs at their resp

Abstract: A control circuit for a photoflash gun capable of fast recycling times, including a flashtube (FT), a switching circuit (SW, L1) for initiating operation of the flashtube, a switch (CR1) in series with the flashtube and switched on at the same time as the flashtube to permit current flow through it, and an arrangement for resetting the switch (CR1) after a predetermined time to cut off current flow through the flashtube. The arrangement comprises an inductance (L2) and a capacitor (C2) coupled to the anode of the switch (CR1), so that when the flashtube is switched on, current discharges through the capacitor (C2), creating a back EMF in the inductance (L2). A voltage of negative polarity is thus developed across capacitor (C2) to switch off switch (CR1) after a predetermined time, thereby to switch off the flashtube. The switch off time is controlled by a light calculation circuit responsive to ambient light.