Abstract: A through-flow electric water heater has a cannister through which water to be heated flows and in which are disposed a first heating means comprising a plurality of electric heating elements and second heating means comprising at least one electric heating element. A control unit comprising a microprocessor receives a first input signal from a flow sensor and a temperature sensor which sense, respectively, the flow rate and temperature of the water flowing into the cannister and switches the plurality of heating elements of the first heating means on and off in different combination to achieve different heating levels and adjusts the level of heat dissipated by burst firing the at least one heating element of the second heating means to achieve a desired total heating level.

Abstract: An air conditioner control system comprises an air conditioner which includes a heating unit, a cooling unit and an internal thermostat, a switch unit for activating the air conditioner and a sensor unit for controlling operation of the switch unit. The sensor unit includes a sound level detecting circuit and an air temperature level detecting circuit and is positioned so as to sense the sound level and temperature level in the room in which the air conditioner is installed.In operation, if the sound level rises above a threshold associated with occupancy of the room, the air conditioner is activated and the heating and cooling units are controlled by the internal thermostat. When the sound level falls below the threshold, after a preset period the air conditioner is activated only when the room temperature departs from a temperature range which is preset in the unit.

Abstract: A current control device for connection in series with an AC load where it is not convenient to make connections in parallel with the load. The device comprises a pair of terminals for connection in series with an AC load, a triac for controlling the flow of current through the load, and a control circuit for controlling the triac. A circuit for supplying current to power supply rails when current is flowing through the load comprises a transformer having a primary winding connected in series with the terminals, and a secondary winding connected across the input of a rectifier, the output of which is connected across the supply rails. A circuit for supplying power to the rails when the flow of current through the load is prevented comprises a resistor bridged by a capacitor connected in series with a zener diode between the terminals, a rectifying diode and a smoothing capacitor.