The telephone repeater circuit or The call signal peripheral circuit to the loud than the original. It’s a circuit that we design follow the request. One of my friends. His ears are a bit tight as such phone rings only. He does not quite go ahead.
Therefore, it is my responsibility, To help design. For the amplify the signal from phone loud sound more than ever. I used to attach circuits with a buzzer or a electric bell, to act as the increase loud sound of bell telephone. For some of you who want to use this a circuit. If it is modified by change light bulb replace the electric bells as well. When the call came in, the lamp will be flashing by the call signal.
The working of a circuit
We connect the input signal directly from the telephone line. However, since a circuit input impedance is very high so it is not loaded the telephone circuit, for enter the call signal to the Q1 work,
Therefore, The collector voltage of Q1 reduced until Q2, and Q3 stops working, The contract of relay is connected to the electric bell and lamps as needed.
How to make it.
This project can build easily by youself. In figure 2 is the PCB layout as real size. and right side is the components layout. Which if you can use the Universal PCB board as well because it has a few parts in circuits.
C1___________0.033uF 600V Polyester Capacitor
C2___________1uF 16V Electrolytic Capacitors
R1___________100K 1/4W Resistor
R2___________100 ohms 1/4W Resistor
R3___________8.2K 1/4W Resistor
R4___________180K 1/4W Resistor
R5___________39K 1/4W Resistor
D1-D5________1N4148 75V 150mA Diodes
Q1-Q2________BC548 45V 100mA NPN Transistor
Q3___________BC337 50V 800mA NPN Transistor
RY___________Relay 12V normal closed
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