Method for completing the connection between a telephone exchange and the phone subscriber's line in response to the reception, at the exchange, of a pre-established code

摘要

A method and apparatus for processing coded information received through a telephone network corresponding to the phone subscriber to complete the connection between the final selector of the network and the subscriber's line only when, at the network, a pre-established code is received. The method comprises detecting the presence of ringing a signal at the phone subscriber's line at the final selector stage of the exchange, opening the phone subscriber's line in response to the detection of the ringing signal, sending from the calling end a code signal, filtering-out the ringing signal and letting through the code characters, decoding the code signal, comparing the code signal with one or more memorized codes, generating a validation signal when a match occurs and closing again the phone subscriber's line only in response to the simultaneous presence of the detected ringing signal and the validation signal. Thus the called subscriber will receive no ringing signal if a right code is not received. Further, the system can be deactivated by transmitting a special code from the subscriber's phone.