PARALLEL
TELEPHONE LINES WITH SECURITY SYSTEM
ABSTRACT
The project is designed to maintain secrecy
among four parallel telephones connected to a single telephone line. When more
than one phone is connected to a single telephone line, anyone can lift a phone
to hear the conversation on the other one. The proposed system provides a
solution for the secrecy among the telephones connected. In order to meet this
requirement we are using 4 telephones connected in parallel through a single
telephone line with each telephone connected through a relay in the system.
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. The microcontroller sends a signal
to a 7 Segment display to display which telephone is lifted, while other
telephones are disconnected by the respective relays with help of a Relay
Driver IC interfaced to the microcontroller. This Project can be used in houses
and offices where more than one telephone is connected in parallel through a
single telephone line. The project is suitable for both incoming and outgoing
calls.
Further
the project can be enhanced by adding more number of phones with an intercom
facility. An incoming caller id facility can also be added to it.
Note: The project needs 4 telephone
instruments to be connected to the board for the functioning of the project.
Telephone instruments are not provided with the kit.
BLOCK DIAGRAM
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