Parallel Telephone with auto secrecy (AT89C2051)

This Project can be used in houses and offices in which more than one telephone is connected in parallel through a single telephone line Our project is used to connect a maximum of four telephones in parallel. When any one of the phone is lifted, all the other lines are disconnected from the telephone line.
The above condition is also applicable when the telephone ring arrives only one telephone which is connected to the telephone line which is lifted first, while the other three lines are disconnected from the telephone line.
All the functions are controlled by the 8 bit Microcontroller AT89C2051 which has a ROM of 2 Kilobytes

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Circuit Diagram:

Downloads:

Download the Source code from here: