INTERCOM

2B-PROJECT SPECIALITIES

This project is a revolution in the field of electronics which is utilized in offices, homes, shops etc.  It is a low cost project.  Here only one switch is used for bell signal as well as sound. Since the circuit is mainly based on one IC, the sound it produces is distinct & clear.

TECHNICAL DESCRIIPTION AND WORKING:-

 

 

This project described here is an intercom project which has been successfully tested.  In this circuit an integrated circuit IC 741 has been used as an Inverting AC Amplifier. The IC 741 is utilised as a pre-amplifier whose input impedence is kept high. A crystal microphone performs the function of high impedence.  The resistance R-3 [2.2] connected in between pin NO. 2 & 6 works as a feed back.  The circuit works on 9 volt DC.  The output of the IC is connected to two transistor TR-1 [BEL 188] and TR-2 [BC 148], which works as a power amplifier. One DPDT [Double Pole Double Through] switch has been used in this project, which, if kept in the first position produces the sound of a buzzer on the other side of the intercom.  When the other man keeps the DPDT switch on “TALK Position” the buzzer sound from the speaker stops and the LEDS on both sides will glow.  When the LEDs glow, the first person knows that the other man on line and talks.  When the conversation is over, the switch is kept in OFF position.

PRECAUTIONS WHILE ASSEMBLING THE PROJECT:

    1. Please mount IC 741 on IC base.
    2. Ensure that the transistor [BEL 188 & BC 148] connections [collector, base and emitter] are proper and not altered.

 

PARTS LIST:-

  1. SEMI CONDUCTORS:-

IC 741 [1 NOS]

TR-1-BEL 188 [2 NOS]

TR-2-BC 148 [2 NOS]

LED – [2 NOS]

CONDENSER MIKE [2 NOS]

  1. RESISTANCE:-

R-3 2.2E [2 NOS]

R-6 180E [2 NOS]

R-2 150K [2 NOS]

R-1, 4 & 5 10K [6 NOS]

R-8 680K [2 NOS]

R-7 2.2K [2NOS]

  1. CAPACITORS:-

C-3, 33MFD/16V [2NOS]

C-2, C-4, 220MFD/16V [4 NOS]

C-1, 403 [.04MF] [2 NOS]

C-5, 103 [.01MF] [2 NOS]

  1. MISCELLANEOUS:-

DPDT SWITCH

BATTERY 9V [2NOS]

CABINET [2 SETS]

FICE CORE WIRE -10 MTR

SPEAKER – 8 OHMS [2 NOS]