Importance

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Abstract

There is provided a telephone toll restrictor which is adapted to split the telephone line into two separate circuits for isolating the instrument from the central office during dialing. A dialing tone sensor provides signalling information to a programmed microprocessor which determines whether or not the number is permissible. A pair of filters separate the high and low frequencies of the tone and input this information to the microprocessor. If the dialing tones are permissible, then a generator regenerates the tones and passes the tones to the central office for completing the call. Furthermore, the telephone line is then recoupled and the call is permitted. If the call is not permitted, then a holding bridge, which holds the central office while the microprocessor examines the number, is opened by the microprocessor, causing the central office to time out, thus denying access to the caller.

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First Claim