This circuit was found in an American documentation from the 1980s. The circuit combines filters of different types in a single structure, each of which can be programmed for a frequency.
We found this circuit in a 1977 National Semiconductor Databook. The circuit can use other FETs...
This circuit from the 80's can be easily implemented but needs some changes to avoid problems with...
We found this 4W transmitter in a Mullard transistor manual from 1960. The circuit is powered by...