This speaker overload protection circuit was found in Radio Electronics from the 1980s. The circuit uses a 9 V relay but can be powered by 12 V for a relay of this voltage.
In the figure we have the way to trigger a 7555 CMOS monostable with a positive pulse. The time...
This circuit is from a 1968 documentation. It generates a non-symmetrical signal with the waveform...
This circuit is from the manual of the used operational amplifier itself. The same setting can be...