Parallel Telephone Line Connection with Secrecy and Call Prevention

Model No. 109: The project is designed to maintain secrecy among four parallel telephones connected to a single telephone line. The proposed system provides a solution for the secrecy among the telephones connected.When any one of the telephone is lifted all other phones are disconnected by the relays through an arrangement of opto-couplers, the output of which is fed to a programmable microcontroller of 8051 family.

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