Importance

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Abstract

A cleaning system for a telephone number list is capable of automatically perform deleting process for null telephone number and updating process for re-writing telephone number list. The cleaning system includes calling portion for transmitting a dialing signal corresponding to each telephone number in a telephone number list to a public telephone network, line monitoring portion for monitoring reaction on the line with respect to the transmission of the dialing signal by the calling portion, effectiveness judging portion for making judgement of an effective telephone number when a ring tone, an off-hook signal prior to detection of the ring tone, within a predetermined period, null telephone number discriminating portion for making judgement that the telephone number checked is null when none of the ring tone, off-hook signal and a busy tone, and outputting portion for generating output lists with distinguishing the effective telephone numbers and the null telephone numbers on the basis of the results of discrimination by the effectiveness judgement portion and the null telephone number.

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First Claim