This filter has a regulated source configuration. It can be implemented with almost any operational amplifier. The formulas for calculating the components are attached to the diagram.
This sensor circuit from a 1967 Ferranti documentation uses components from the era. The circuit...
This is the receiver for the previous circuit transmitter. Similarly, no information about the...
Found in a 90s Popular Electronics, this circuit uses two PLL tone recognizers to trigger by touch an...