Shown on this slide is an ACS or ACST, the most rugged types of AC switches as mentioned previously. Illustrated is a standard Triac, which normally would have a voltage protection, overvoltage protection device called a MOV or a varistor. Added to this is a snubber, a capacitor and a resistor located across the main terminals of the AC switch. The snubber with the RC as shown is used to protect against dV/dt high voltage transients which are very fast. The MOV is used to protect against overvoltage, it clamps the voltage across the main terminals of the device. This would be an example of a standard four-quadrant Triac. If the user would prefer snubberless features, they can use a snubberless Triac without the RC connection shown because the snubberless Triac does not require this type of dV/dt protection; it has its own high-noise immunity. Moving to an ACST, the varistor and the RC snubber are not needed because an ACST is constructed in such a way that it has internal protection and internal, built-in noise immunity to dV/dt, which allows it to be used in very demanding applications. Further, if the designer wants a version of the ACS which is driven by a microcontroller and the current into the gate is very limited, ST has an ACS version of the ACST which has its own internal gate amplifier, as shown in the diagram, which allows the use of a very low trigger current from the microcontroller output port.