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.
- Direct supply telephone signal from telephone line to the point where coil L1 is connected as shown in figure 2.
- Or connect this peak up coil L1 and so adjusted near telephone set where excellent voice be able to single out.
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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