•  
  •  

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.

If there are any problems please contact webmaster@electronic-circuits-diagrams.com

Please share & like


600pcs 15Value NPN PNP Transistor TO-92 Assortment Kit Set W/Box new picture

600pcs 15Value NPN PNP Transistor TO-92 Assortment Kit Set W/Box new

$11.12



20, 50, or 100pcs 2n2222A General Purpose NPN Transistor TO-92 USA SOLD/SHIP picture

20, 50, or 100pcs 2n2222A General Purpose NPN Transistor TO-92 USA SOLD/SHIP

$5.25



20, 50, or 100pcs Unbranded 2N3904 General Purpose NPN Transistor TO-92 GENERIC picture

20, 50, or 100pcs Unbranded 2N3904 General Purpose NPN Transistor TO-92 GENERIC

$1.99



100pcs 2n3904  NPN Transistor TO-92 SOLD/SHIP USA picture

100pcs 2n3904 NPN Transistor TO-92 SOLD/SHIP USA

$4.90



' TIP122 (2 pcs) Transistor - from USA picture

' TIP122 (2 pcs) Transistor - from USA

$2.95



AC127 GERMANIUM TRANSISTOR picture

AC127 GERMANIUM TRANSISTOR

$1.68



' 2N2222A (10 pcs) 2N2222 TO-92 NPN Transistor - from USA picture

' 2N2222A (10 pcs) 2N2222 TO-92 NPN Transistor - from USA

$2.95



150pcs 15Types Transistor TO-92 Assortment Kit C1815 2N5551 S9018 S9013 C945 picture

150pcs 15Types Transistor TO-92 Assortment Kit C1815 2N5551 S9018 S9013 C945

$6.95



600pcs 15value (A1015 - 2N5551) Bipolar Signal Transistor TO-92 NPN PNP DIY kit picture

600pcs 15value (A1015 - 2N5551) Bipolar Signal Transistor TO-92 NPN PNP DIY kit

$11.18



TO-92 Assortment NPN PNP DIY kit 15 value 600pcs Transistor  picture

TO-92 Assortment NPN PNP DIY kit 15 value 600pcs Transistor

$13.09