Found in a 1964 Electronic Design this circuit compares two signals by providing the inverse of the algebraic sum of their frequencies. The circuit can be made with modern equivalent transistors.
With this circuit, from a 1991 publication, it is possible to regulate the output of a symmetric source...
Found in old documentation, this circuit is tuned to pass signals below 245 Hz with a level of...
Found in an Electronic Design from the 90s, this circuit produces a signal whose frequency is...