| 摘要 |
PURPOSE:To allow only an incoming call from a desired party by an incoming side subscriber by installing an adaptor corresponding to a subscriber of an incoming side subscriber line exchange and allowing the adaptor to receive and collate ciphered information inputted from an outgoing subscriber in the tentative respnse state at incoming call. CONSTITUTION:The ciphered information comprising dial signal (PB signal) of a pushphone transmitted from the outgoing telephone set 1 is transmitted to the adaptor (ADP) 6, received by a PB signal receiver 7 and its output is transferred to a CPU13. The ciphered information to select an opposite party allowing the incoming call registered in advance by the incoming subscriber is stored in a memory 14. The CPU13 compares the ciphered information transferred from the PB signal receiver 7 with the ciphered information stored in the memory 14 and when the both are coincident, it is regarded as an incoming call from the opposite party allowing the incoming call for the incoming subscriber, a relay A17 is activated, the contact (a) is driven downward, a call signal is transmitted to the incoming telephone set 24 from a call signal transmission circuit 15, then an output 20 of the CPU13 activates a call tone transmission circuit 10 so as to transmit the call tone to the outgoing side. |
