This circuit was found in the May 1990 Radio Electronics magazine. The timings depend on the capacitors and the supply voltage depends on the relay used.
This is the project found in a 1981 publication, but it is still viable. It is a simple AM...
This commercial earphone receiver was manufactured in the 1960s in Japan. It was powered by a 9 V...
This circuit was found in a European publication from the 1980s. The transistors can be the BC548...