This circuit was found in documentation from the 90s. The transistors can be general-purpose equivalents. The circuit has two versions, one that drives LEDs and another that drives a relay as a load.
Found in Popular Electronics from the 1980s, this circuit can use more modern transistors such as...
This circuit is from a Radio Electronics from February 1970. The integrated circuit is an...
This is stage is transformer coupled and was found in na old publication of the year 1958. The...