Abstract: In a power-operated valve in which the pressure of a working fluid is used to control the opening and closing of the valve member in dependence on the condition of an integral power-operated bleed valve, a compensation passage being formed in the valve member to permit working fluid to close the valve when the bleed valve is closed, the compensation passage is formed in that area of the valve member which is bounded by the valve seating and which also defines the cross-sectional area of the inlet chamber, whereby the closing force on the valve member is proportional to the area of the valve housing, thus enhancing the sensitivity of the valve. In a preferred embodiment, a filter is incorporated in the valve member to filter the working fluid to the compensation passage without filtering the bulk of fluid passing through the valve.

Abstract: A time switch (100) comprises terminals (110) spaced around a slip ring (108) connected to a voltage source (V). A motor (104) drives a brush (102) to sequentially connect the terminals (110) to the slip ring (108) to energize the terminals in sequence. Each terminal (110)--as shown for one of them designated 112--is connected via a respective transistor (116) and manually operable switch (124) to a pair of common output conductors or bus-bars (130, 132), whereby for each successive period of time corresponding to each successive terminal (110) being energized the conductors (130, 132) are energized in accordance with the setting of a respective one of the switches. Thus, a desired time-varying pattern of energization of the conductors (130, 132) to accomplish a control function, e.g. the control of a central heating system to provide different heat outputs at different times of the day, can be set up at will simply by adjusting the various switches (124).

Abstract: A control arrangement is provided for a heating system having heat outlets each controlled by a solenoid valve (210). Each heat outlet is connected to a pair of thermostatic switches (411, 413) operative at different temperatures. A time switch included in a central control means (108) is operative to selectively energize a pair of bus-bars (530, 532) at different times, thereby to provide common output signals for actuating the heat outlets via different thermostatic switches (411, 413) at different times to provide different heat outputs during different parts of a predetermined period of time (e.g. 24 hours). The central control means (108) includes a plurality of manual switches (540) each connecting the time switch output bus-bars (530, 532) to the thermostatic switches (411, 413) of an associated one of the heat outlets to manually set the heat output of the heat outlet.