Found in a 1990 Hobbyst Handbook this circuit has an output power of a few tens of watts and serves as reinforced for the car's sound. The speaker can be 2 or 4 ohm.
This well-known circuit triggers a relay when light striking the phototransistor is cut off. The...
Found in the September 1982 issue of Radio Electronics magazine, this circuit triggers a relay...
This circuit was found in a 1985 English magazine, but it can still be easily assembled, as the...