Schematics > Audio > Low cost intercom using transistors
Low cost intercom using transistors
The circuit comprises a 3-stage resistor-capacitor coupled amplifier. When
ring button S2 is pressed, the amplifier circuit formed around transistors T1
and T2 gets converted into an asymmetrical astable multivib-rator generating
ring signals. These ring signals are amplified by transistor T3 to drive the
speaker of earpiece.
Current consumption of this intercom is 10 to 15 mA only. Thus a 9-volt PP3
battery would have a long life, when used in this circuit.
For making a two-way intercom, two identical units, as shown in figure, are
required to be used. Output of one amplifier unit goes to speaker of the other
unit, and vice versa. For single-battery operation, join corresponding supply
and ground terminals of both the units together.
The complete circuit, along with microphone and earpiece etc, can be housed
inside the plastic body of a cellphone toy, which is easily available in the
market. Suggested cellphone cabinet is shown.
Title: Low cost intercom using transistors
Source: www.electronic-circuits-diagrams.com
Published on: 2005-02-01
Reads: 519
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