Abstract: A flush mounted installation unit in which an operating portion of the installation unit such as the supporting plate, the covering or switch unit is designed as an antenna so that the unit can perform the dual function of housing and mounting the components for use in a control system and providing an antenna for a radio link between the central control unit and the components.

Abstract: A system for the control of a load such as a heating or cooling plant in response to changes in an external parameter, specifically ambient temperature, comprises a loop circuit with two conductors connected at an input end across a power supply and at an output end across a switching network, the load being inserted in one of these conductors. A high-impedance voltage multiplier connected across these conductors downstream of the load, in parallel with the switching network, supplies the necessary operating voltage to a parameter sensor such as a thermostat even when that network is in a low-impedance state so as to draw a maximum load current. The switching network may include a voltage clamp provided with a source of reference potential, e.g. a primary battery, which upon failure of the normal power supply can act as a standby supply insuring continued operation of a timer serving for a periodic switchover between different temperature thresholds for the thermostat.