This circuit was found in a Popular Electronics from the 90s. The counter circuit is not common today. The circuit can be programmed for hourly intervals, according to the values of R4 and C2.
This is stage is transformer coupled and was found in na old publication of the year 1958. The...
This circuit is from the magazine 73, for radio amateurs, from the 80s. The circuit uses common...
This indicator circuit used and game machines (arcades) to indicate that the machine is being...