Importance

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Abstract

A unit price setting arrangement for differently priced products available from a remotely located dispenser for example, grades of fuel, from a pump, consists of a central transmitter and a receiver in each dispenser. The transmitter forms a series of fixed length binary words, one for each product, and transmits them in sequence repetitively. Each receiver counts words of the sequence received and compares them with the position of a selected product in the sequence to determine which word relates to the product of interest. That word only is used and is applied to a comparator with a corresponding word stored from a previous transmission to detect a change in the word. A shift register having a stored bit responds to an unsuccessful comparison to shift the bit through one location and a shift through a predetermined number of locations by successive unsuccessful comparisons, if the change is permanent, causes a controller to replace the stored value with the newly received one. The shift register is reset by a correct comparison if the change indicated by the comparison is not sustained and the stored value is unaltered. Thus any disturbance giving rise to a wrong binary word is ineffective but a deliberate change repeated over several transmissions is effective.

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First Claim