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 V_CCis given to IC₁through 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 L₁is 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.

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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