Diodes D2 via D5 connected in bridge configuration constitute a polarity guard to ensure that the amplifier is powered with correct polarity, irrespective of the line polarity, Zener diode D1 might have any breakdown voltage between 6 and 12 volts range. This audio signal is put to use as input for IC LM386. As original secondary (output) winding is connected in series with the phone lines, the speech signals passing through the lines cause alteration inside the magnetic flux in the core of transformer and thereby induce signal voltage across the primary winding. Transformer X1 can be a transistor radio”s output transformer used in reverse. ![]() ![]() Diodes D6 and D7 are implemented to limit the input signal strength. ![]() A volume control for this telephone amplifier is included to adjust the volume as desired.
0 Comments
Leave a Reply. |