This circuit is from a manual from the 80's and the operational one used, uncommon nowadays, can be replaced by a modern equivalent. The power supply must be symmetrical.
We found this circuit in the May 1990 issue of Radio Electronics magazine. The circuit is powered by...
When the light that falls on the LDR is cut off, this 1992 circuit activates a relay for a set...
This siren produces an intermitent sound given by the characteristics of the two oscillators using the...