Importance

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Abstract

A miniaturized card unit, resembling a standard credit card, incorporates solid state counter, a multiplexer means, and a small battery. The counter may be incremented or decremented in accordance with a direction control signal. A multiplexer in the card unit is releasably engageable with the demultiplexer provided in a card reader unit. Control signals, simultaneously applied to the multiplexer and demultiplexer transfer the count stored in the card unit to decoder driver circuits which drive a display for visually displaying the decimal count stored in the card. A logical circuit monitors selected segments of the display to enable operation of the device controlled by the card reader unit so long as the card inserted therein contains a non-zero count. The logical circuit prevents operation of the device upon the occurrence of a zero count as well as the absence of a card unit. A relatively low frequency clock is utilized to control the illumination of the card reader display as well as the generation of the multiplexing signals. Signals representative of the device usage are applied to the card unit counter for decrementing the count. A new count is introduced into the card unit by insertion into a card programmer unit having settable thumbwheel switches for setting a down counter. The presence of a card unit and the closure of a program switch causes simultaneous incrementing of the card unit counter and decrementing of the card program counter. When the card programmer unit counter is decremented to zero, incrementing of the card unit counter is automatically terminated. The card programmer unit display visually displays the count in the card unit counter confirming that the desired count has been placed in the card unit, said display incorporating demultiplexer, driver and control circuits similar to those provided in the card reader unit. The use of cascaded gating means prevents false count pulses from being transferred to the card unit counter when the end count is reached.

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First Claim