Obtained from a 1969 documentation, this circuit can operate at frequencies up to 500 Hz, counting up to 999. The circuit makes use of neon lamps of the time.
The cut-off frequency of the filter shown in the figure can be adjusted to values between...
This circuit was found in a Popular Electronics from the 90s. The components used are all common...
This circuit uses a dual floodgate MOSFET not very easy to obtain today. Its handling is very...