Found in documentation from the 1980s, this circuit uses an operational amplifier from that time. Transistors are also from the era, and general-purpose equivalents can now be used.
This circuit modifies the logical level of a digital function by switching to TTL, for example....
This source, obtained in a 1973 publication, uses a low power transistor to regulate the output...
This circuit with Triac causes an ordinary incandescent lamp to flash rapidly at a frequency set...