| 摘要 |
<p>1425803 Ripple control receivers ZELLWEGER USTER Ltd 24 April 1974 [13 July 1973] 17879/74 Heading G4H A ripple control receiver includes means 44- 48 for preventing faulty operation in the event of mains failure. As shown, mains voltage U N with a superimposed signal U S is rectified at 7 and filtered at 20 to provide signal and reference frequencies f, S f N which are compated (25, 32) at 26, an on/ off signal being provided at outputs 33 or 34 thereof for controlling a relay 41 operative to connect or disconnect a load 36 to or from the mains 6. A capacitor 44 is kept fully charged by means of a resistor 46 until a mains failure, when diode 48 conducts and capacitor 44 energizes 20, 26 while it discharges. The voltage level at which 20, 26 (which may be integrated circuits) cease to operate reliably is arranged to be less than the minimum voltage level required to operate relay 41 so that false switching of load 36 never occurs.</p> |
