This circuit was found in the Electronics Experimenter Handbook from 1991. The circuit controls a simple relay for the purpose of turning circuits on or off or switching audio channels.
An advanced motor control software plug-in for Microchip’s MPLAB® X Integrated Development...
This relay without lock uses a general-purpose transistor. The relay is according to the supply....
This signal follower is from a 1970's documentation. So it uses the traditional configuration at the time...