TSS( Thyristor Surge Suppressors ), also known as surge suppressor thyristor, is PNPN device of four-layer structure made by semiconductor technology, whose volt-ampere characteristics are similar to thyristor and have typical switching characteristics. TSS owns accurate on-voltage, fast response, super surge absorbency, low capacitance, bidirectional symmetry and various encapsulations (SMA, SMB, DO-15, TO-92 , etc.) with meeting different installation space requirements. Generally, it is parallel in the circuit application.

In the normal operation of the circuit, TSS is in the cut-off state. When abnormal overvoltage occurs in the circuit due to induction thunder and operation overvoltage, TSS quickly conducts and releases abnormal overcurrent caused by abnormal overvoltage, thus protecting the back-end equipment from abnormal overvoltage damage. After the abnormal overvoltage disappears, TSS resumes to the cut-off state.