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Simple Telephone Amplifier Circuit Diagram


The output telephone signal is more powerful then the signal fed to base of the transistor T1. The output signal from transistor T1 is fed to pin no 3 of power amplifier LM386 which amplify up to necessity level and output is obtained from pin no 5 is fed to speaker through capacitor C9. The VCC is given to IC1 through pin 6. The telephone signal is fed in to circuit through two ways.
  1. Direct supply telephone signal from telephone line to the point where coil L1 is connected as shown in figure 2.
  2. Or connect this peak up coil L1 and so adjusted near telephone set where excellent voice be able to single out. 
Simple Telephone Amplifier Circuit Diagram
    Simple Telephone Amplifier Circuit Diagram

    PARTS LIST

    Resistors (all ¼-watt, ± 5% Carbon)

    R1 = 100 KΩ
    R2 = 39 KΩ
    R3 = 2.2 KΩ
    R4 = 680 Ω
    R5 = 100 Ω
    VR1 = 4.7 KΩ
    VR2 = 10 KΩ

    Capacitors

    C1 = 27 KPF (273)
    C2, C4 = 2.2 µF/16 V
    C3 = 22 µF/16 V
    C5, C10 = 100 µF/16 V
    C6 = 10 µF/16 V
    C7 = 100 KPF (104)
    C8 = 47 KPF (473)
    C9 = 220 µF/16 V

    Semiconductors

    T1 = BC147B
    IC1 = LM386 power amplifier

    Miscellaneous

    L1 = Pick up Coil
    Speaker 8Ω
    SW1 = On/Off switch



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