Centra-burkle Gmbh & Co.

Gunther Weimer

Henning Becker

A system for alternately activating and deactivating a load comprises a high-resistance d-c circuit branch connected across a power supply downstream of a load-operating impedance, this branch including a voltage limiter and a voltage multiplier in series with each other and with a switching stage responsive to commands from a timer and/or a parameter sensor such as a thermostat. The junction of the voltage limiter and the voltage multiplier is connected to one input of a differential amplifier whose other input is energized with either of two potentials, respectively higher and lower than that of the junction, by the switching stage. The amplifier output controls a variable-resistance element, such as a transistor of the bipolar or the MOSFET type, connected across the high-resistance branch to form a current path in series with the load-operating impedance, the resistance of this path being variable between a high value minimizing the flow of load current and a low value sufficient to maintain the switching stage operational. A standby source may be provided for keeping the switching stage or at least an electric timer thereof energized during interruptions of the main power supply.

Switchover system for binary load control

In order to ascertain the magnitude R.sub.i of an unknown resistance element in digital terms, two calibrating resistances of known magnitudes R.sub.1 and R.sub.2 =mR.sub.1 (with m&gt;1) are connected in circuit with a capacitor, to form a switchable RC network, during two gating periods whereas the unknown resistance element is inserted in their place during a third gating period. A multiplicity of counting pulses are fed during each gating period to a pulse counter delivering their count to an arithmetic unit which determines the ratio R.sub.i /R.sub.1 from the several pulse counts and from the factor m. The switchable RC network may be part of a one-shot pulse generator, establishing a variable gating period for counting pulses of a fixed cadence, or of an astable multivibrator generating different counting pulse rates during gating periods of constant duration. The fixed pulse cadence or the constant gating periods are established by another RC network which may share a common coincidence (AND, NAND or NOR) gate with the switchable network.

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Gerlingen, Germany

Gunther Weimer