This circuit synthesizes the tick of a metronome with the speed controlled in RV1. The circuit is powered by a 12 to 15 V source. The transistor may be the BC548 and it seems to us that, due to the symbology adopted, the zener diode Z1 is inverted. The circuit output must be applied to the input of an amplifier. Remember the 741 power pins not shown in the diagram. The circuit is from a 1979 British magazine.
