The circuit is from a June 1995 Electronics Now. The relay is power-dependent and both R1 and R2 should have close resistances in operation.
This TTL circuit is from a Radio Electronics magazine from February 1973. The circuit must be...
Common operational amplifiers like the TL series, CA3140 and others can be used in this circuit...
This circuit uses only two common transistors and provides good audio power in a speaker. Readers who...