The circuit diagram shows the over voltage protection as a feature of LM317 linear voltage regulator.Over voltages come from several source or factors which are usually in the form of transients. Transients are represented in spikes which are short and fast disturbance or change in the voltage and current component. It only occurs in circuits containing conductance and capacitance. The causes are typically from power outages, short circuits, tripped circuit breakers, lightning spikes, inductive spikes and other malfunctions from power company. As an example using a 12V battery source, the LM317 voltage regulator can be used to obtain 6 Volts. To protect any device from over voltage, there are ways such as adding relays or a zener diode. A relay switch functions by opening or closing under the command of another circuit. But finding a relay that would limit the output from 6 V to 12 V is not easy. Fortunately, zener diodes are more abundant. A 6.2V zener diode rating can be used t...