This circuit was obtained in a Popular Electronics of the 90s. The circuit uses integrated from the time, uncommon today. Note that the speaker has a higher impedance than ordinary speakers.
This two-port monostable of the 4001 was suggested by an article in the April 1988 Radio...
We found this circuit in a documentation from the 70s. Semiconductors are from the era and can be...
This circuit is from 1992 documentation. The transistor can be a TIP42 with a good heat sink for...