Abstract: Apparatus and method is provided wherein power pulses are supplied from a standard meter to a supplementary data accumulating means associated with a meter under test. Data accumulation means in the supplementary data accumulating means and in the meter under test are set to a known value and both meters are subjected to similar voltage and current values. A stop signal is generated when the supplementary data accumulating means reaches a predetermined value N and the value in the meter data accumulating means is latched. The stop signal causes arithmetical division of the latched value by N to form a quotient value and is entered into a reference value memory in the meter under test, the reference value memory value determining the number of pulses per unit power pulse generated by the meter.

Abstract: A method for generating a product of signals proportional to the voltage of an electrical supply and the current flowing through a load connected thereto, comprises the steps of deriving a first signal proportional to the said supply voltage, deriving a second signal proportional to the load current, frequency modulating two constant frequency carrier signals by the said first and second signals to produce third and fourth signals respectively, normalizing the third and fourth signals with reference to frequencies corresponding to zero voltage and zero current, and multiplying the two normalized third and fourth signals to form a product signal which is proportional to the power being absorbed by the load connected to the electrical supply. The third and fourth signals comprise pulse trains whose instantaneous pulse repetition rate is proportional to the voltage and current. Apparatus is described for performing this method. A 555 timer device is employed for voltage to frequency conversation.

Abstract: The invention relates to an apparatus for protecting electronic circuitry against interfering high voltage discharges, the electronic circuitry being of the nature which controls the operation of a meter. A memory is provided on which a pattern of signals is stored by a watchdog circuit. When an orderly shutdown of the controller occurs, for example due to credit expiry, and when the controller is restored to power, the watchdog circuit reads the memory and generates a shutdown control signal if the stored signal pattern is not preset in the memory.

Abstract: A card reader having a card reading mechanism, a card perforating device and a card erasure mechanism, wherein the erasure mechanism comprises a permanent magnet movable by means of a pivoted arm towards and away from a card erasure position, and a drive means for the magnet arm which is coupled to a motor drive for the perforating device.