Importance

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Abstract

A circuit which prevents a telephone station from being used for unauthorized toll calls while allowing toll calls to be made when preceded by authorized passwords. When the telephone station is in the toll restriction mode of operation a microprocessor disconnects the tone generator from the keypad and provides audible and visual error signals upon detection of operation of the '0' or '1' keypad buttons. Upon detection of simultaneous operation of the '1' and '2' keypad buttons, the microprocessor provides audible and visual signals to prompt entry of a password. If a valid password is entered, the telephone station enters the unrestricted mode of operation and the toll restriction circuit is disabled until the handset is returned to the on-hook position after termination of the subsequent toll call. Upon detection of prolonged operation of the '1' keypad button, the telephone station enters the password update mode of operation and the microprocessor provides visual and audible signals to prompt entry of the old password followed by a double entry of the new password to ensure correct entry of that new password.

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First Claim