We found this circuit in the Radio Electronics magazine of May 1977. The transformer voltage is 6 + 6 V, and the current depends on the zener diodes and is in the order of 100 to 200 mA.
Found with variations on this site, this circuit was taken from an American documentation from the...
This circuit generates damped sounds imitating a drum or other percussion instrument with...
This is the traditional configuration for a limit comparator or window comparator, using two...