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This simple CPO is for those who want to practice Morse Code in a different way, ie with out the morse key. It can be also used as a touch operated door bell.
The popular timer IC555 is wired as astable multivibrator. The frequency (tone) can be changed by varying the 100 K variable resistor between pin 7 and 6 of timer IC555. The volume can be changed by varying the 10 K variable resistor and the sensitivity of touch plate can be controlled by adjusting the 1 K Ohms preset at pin 4 of IC555.
The touch plate is connected to the base of transistor BC147B. Many touch switches restrict the size of the touch switch. In this circuit the length of wire between the base of the transistor and the touch plate is not critical. In prototype i used 9 cm wire and 3 x 6 cm 3mm thick aluminium plate for touch plate.
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