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Easy Loudspeaker Circuit For Telephone(BC548 )

2016-02-01 17:16  
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This paper introduces the Easy Loudspeaker Circuit For Telephone (BC548). This principle is easy to understand, but also very practical. Depth understanding of circuit elements, can be more effective to grasp this principle. Do you know the circuit, for example, can understand and buy these components: BC548 , Sl100.

This below circuit is a easy handsfree telephone receiver system. This doesn’t have dialing circuit so, it’s not a total phone replacement circuit, but it’s just only a loudspeaker system (i.e, phone receiver,not dialer). This is a easy circuit with all parts easily available, and without any complex I.C. It is made of just capacitors, diodes, resistors, and transistors. This circuit can be made within 70 rupees and it compromises of the following sections,

Figure:1 Circuit diagram

Figure 1 Circuit diagram

Power rectifier and filter section
This section is made of a simple bridge rectifier and a indicating powerLED.Voltage regulator section
This section is made upon transistor Sl100, which is a general purposeNPNtransistor in metal package. That is used to regulate voltage at a level of 9 0.6=9.6V by a 9V zener diode.Speaker output section
This section contains a high impedance speaker and two BC548NPNtransistor to amplify the signal from line, the input of the 548 transistor pair is fed with a linear or pot control of 10K for volume adjust.Microphone input section
This section contains a condenser microphone (tablet) and two BC548NPNtransistor to amplify the signal from mic, the output of the 548 transistor pair is fed with a linear or pot control of 10K for volume adjust to the line. 

 


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