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.
We found this circuit in a 1967 General Electric SCR manual. The time is set to R1 and depends on C1...
This circuit uses an ignition coil to generate the high voltage that electrifies a fence. However, in...
Found in an older Radio Electronics, this circuit generates signals that can be used with regular...