Found in a 1967 General Electric documentation this circuit uses unijunction transistors that may be equivalent to those indicated. The number of stages can be modified.
This circuit was found in a 1980 publication, but it can be assembled using a BD135 for Q1 or even...
Constant current sources are used in applications such as battery chargers, electrolytic tanks, etc....
This circuit appears in other articles in this section and even in other sections of the site....