This circuit is from the 80's but uses common components today. The relay is voltage sensitive according to the power supply used. Transistors may be general purpose types.
Found in a September 1992 Radio Electronics magazine article, this circuit generates a pulse as...
This simple latching alarm circuit using CMOS gates was found in the May 1990 Radio Electronics magazine....
This analog volt-ammeter was found in an Electronics World of 1968. It makes use of a 0-1 mA...