The frequency of each note depends on R2, which must be replaced by a keyboard. The circuit is from Radio Electronics from April 1980. The power supply is 9 V for the amplifier used.
This circuit for monitoring telegraphy transmissions was found in a 1975 CQ magazine. Transistors may be...
The integrated circuit used in this application is like the 555. The components depend on the...
The circuit presented is a simple MW tuner that can be plugged into the input of any audio...