This filter for receiving audio in telegraphy was found in a magazine 73 for radio amateurs, in an edition of the 80s. The circuit is tuned to 700 Hz and has a 200 Hz bandpass.
This circuit was found in an Electronics World of 1969. Transistors are general-purpose types. It...
It is like to the previous circuit with a lock that keeps the LED on at the end of the timer. The...
This good quality audio amplifier with an output of about 10 W with the original transistor was...