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 assumes that a pulse produced by S1 has a constant duration determined by R1 and C1....
This circuit was obtained from an ancient American documentation. The coil consists of 80 to 100...
This circuit was found in Raytheon's 1967 documentation. The circuit uses an operating of the era,...