Found in old documentation, this circuit is tuned to pass signals below 245 Hz with a level of 0.044 dB above 500 Hz.
We found this circuit in an English publication in 1982, but it can still be easily assembled by...
This circuit was obtained in a 1967 General Electric documentation. It alternately fires two xenon...
This is a traditional flasher configuration with two neon lamps. The frequency is given by the 100 nF...