Found in an old Popular Electronics this circuit appears in other variations on this site and in this section. It uses a 7-segment common anode LED display as an indicator.
This circuit can be applied to several logics. The circuit is from an Electronics Now from the...
This simple circuit with SCR and unijunction transistor appeared in Radio Electronics magazine in July...
This timer was found in a 1980 publication. With the BC548 for Q1, an 8-ohm speaker with 6 V power...