In this phase shift circuit, the transistor can be any general-purpose transistor. The circuit is from an Electronics Now issue of June 1993.
In this circuit, obtained from a 1979 publication, IC1 is a 555 and IC2 is a 4020. The transistor is the...
The presented circuit uses a window comparator to keep a relay activated only when the sensor is...
Similar circuits can be found on this site. This is from an 80's American documentation. The...