| 摘要 |
A card wallet that can detect a missing credit card or driver's license is described. A wallet for holding plastic cards records electronically the addition of cards as well as the removal of cards. Whenever the number of cards in the wallet is less than the recorded number of cards, a signal is sent to the user warning the user that a card is missing. This may be the result of leaving a credit card at a checkout counter, theft, mishandling, or loss. The warning signal is issued only a short time after the last card was removed, aiding in rapid investigation and recovery. A simple method of detecting a missing card is to add the number of incoming cards and subtract the number of outgoing cards. An arrangement of momentary switches is used to determine the direction that the card is moving in the wallet.
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