This circuit was found in the August 1993 Electronics Now magazine. It is for telephones used on common old-style analog lines.
This interesting constant current source circuit was found in the September 1989 issue of Radio...
We find this circuit in a 1970 publication. Transistors can be replaced by current equivalents and LDR is...
Employing a unijunction and a triac of the era, this 1964 Electronic Design circuit uses a diac to...