This circuit is from 1970 documentation. The SCRs are types of the era that can be replaced with 106 Series equivalents. The circuit is powered with 100 V dc.
Found in a PE Hobbyst Handbook of 1991, this circuit was originally proposed to time photographic...
In this circuit of 1987 the player has to briefly press one of the keys trying to hit which LED...
This circuit with a double-gate MOS transistor was found in a Popular Electronics from the 90's....