This regulator can be controlled by a logic signal. The circuit is from an Electronics Now from the 90s. Note that the switching transistor is before the integrated circuit.
This simple intercom for home use was found in a 1979 publication. It can be easily mounted with...
This circuit was found in a Popular Electronics from the 90's. The CMOS integrated circuit used is...
This circuit was found in old Maxim documentation. Check the availability of the IC if you are...