Telephone Amplifier Circuit

Telephone talks are meant to be private or kept in between two persons engaged in the conversation. But, sometimes it is also necessary to have a group talk. The project entitled Telephone amplifier circuit serves us right. It is very simple, yet inexpensive and useful which uses very common power amplifier LM386 and some more components. The circuit can be used to produce loud sound to discuss or start a conversation in a group through telephone.

Working of the  Telephone Amplifier Circuit

The signal emitted as output from telephone 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 amplifies up to a level required and then the output obtained from pin no 5 is fed to speaker through capacitor C₉. The V_CC is given to IC₁ through pin 6. The telephone signal  can be 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.

Check out other telephone related projects posted in bestengineeringprojects.com

1. Add on Device For Telephone
2. Telephone Converter Circuit
3. Automatic Time Indicator for Telephone
4. Telephone Spy
5. Telephone Ringer Circuit using 555 IC

PARTS LIST OF TELEPHONE AMPLIFIER CIRCUIT

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) (Ceramic Disc)

C₂, C₄ = 2.2 µF, 16V (Electrolytic Capacitor)

C₃ = 22 µF, 16V (Electrolytic Capacitor)

C₅, C₁₀ = 100 µF, 16V (Electrolytic Capacitor)

C₆ = 10 µF, 16V (Electrolytic Capacitor)

C₇ = 100 KPF (104) (Ceramic Disc)

C₈ = 47 KPF (473) (Ceramic Disc)

C₉ = 220 µF, 16 V (Electrolytic Capacitor)

Semiconductors

T₁ = BC147B (NPN Silicon Transistor)

IC₁ = LM386 (power amplifier IC)

Miscellaneous

L₁ = Pick up Coil

Speaker 8Ω

SW₁ = On/Off switch