A receiving circuit stops a one shot timer from generating an output signal immediately after the output signal is outputted to an external entity until a predetermined stretch time elapses. The discharge vessel encloses a discharge volume and comprises two electrodes and contains a filling. When there is an interruption in the mains power from the grid, the dchp switches into a grid independent mode wherein power is generated by the dchp and is supplied to a controller 26 and to a water pump so as to maintain integrity of heat supply to the dwelling; the remaining power after that is supplied to selected domestic electrically powered equipment such as lights or television sets. 900 gcm3 and a melt flow rate, at 190\xb0 C. The temperature at which an oscillation threshold current is minimized is 60\xb0 C.