Diacs are bi-directional diodes that switch AC voltages and trigger silicon controlled rectifiers (SCRs) and triacs. Except for a small leakage current, diacs do not conduct until the breakover voltage is reached.

Gate turn-off thyristors (GTOs) are four-layer PNPN devices that act as switches, rectifiers, and voltage regulators. Like other thyristors, GTOs can be turned on by the application of a positive gate signal (g > 0); however, unlike other more conventional devices that can be turned off only at a zero crossing of current, GTOs can be turned off at any time by the application of a gate signal equal to zero.

Programmable uni-junction transistors (PUT) are three-terminal thyristors that are triggered into conduction when the voltage at the anode exceeds the voltage at the gate. The PUT is similar to the UJT, but its intrinsic standoff ratio can be set by two external resistors. Hence, the term "programmable" is used.

Quadracs are a special type of thyristor which combines a diac and a triac in a single package. The diac is the triggering device for the triac.

Sidacs are bidirectional silicon switches that provide greater power handling capabilities than standard diacs. These four-layer (PNPN) semiconductor devices are triggered by thyristors and act as open circuits that are capable of withstanding a specific rated voltage until triggered.

Silicon controlled rectifiers (SCR) are four-layer (PNPN) thyristors with three terminals: an input control terminal (gate), an output terminal (anode), and a terminal common to both the input and output (cathode). SCRs are used mainly with high voltages and currents, often to control alternating current (AC) where the change of sign causes the device to switch off automatically.

Thyristor surge suppressors are semiconductor chips used to protect circuits and devices from over-voltage and over-current.

Thyristors are a class of four-layer (PNPN) semiconductor devices that act as switches, rectifiers, or voltage regulators.

Triacs are three-terminal silicon devices that are configured in an inverse parallel arrangement to provide load current during both halves of the AC supply voltage. They are often used to control motor speed.

Unijunction transistors (UJT) are three-terminal devices that exhibit a negative resistance characteristic.