| 摘要 |
PROBLEM TO BE SOLVED: To protect the privacy of originator and to enable the police and a telephone service company to decode a cipher so as to detect an originator, where a receiver suffers from a criminal act by enciphering and displaying a calling telephone number entirely or partially, on a called side telephone number displaying device. SOLUTION: A calling side subscriber line exchange 12 sends calling telephone number data with an address massage including it to a called side subscriber line exchange 13 via a common line signal network. It is to a telephone number enciphering device 16, to which is a cipher storage device 15 is connected, via a common line signal device 138 an a call control processor 137, the four lower digits of the calling telephone number data are converted into implication based on a conversion character table that has been stored preliminarily in the device 15, enciphered data is sent to a calling telephone number transmitting device, it is made a signal form that can be received by a called side, it is sent to a called side telephone set 10 via a subscriber line 131 and the enciphered data is shown here. Here, the conversion charter table is stored by a telephone service company, etc., and the cipher is decoded by it when necessary.
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