Thyristors are commonly used in control and automation applications due to their simplicity and great power handling capability, DIACs and SIACs are two-terminal electronic devices that conduct current in both directions and are turned on when the voltage across their terminals reaches the breakover voltage. SCRs and TRIACS are three-terminal devices whose turn on is controlled through the gate terminal, SCRs conduct current in a single direction as rectifier diodes while TRIACs conduct current in both directions and are typically used to switch AC loads.