P61089 Series Thyristor Surge Protection Device, TSS is a PNPN type device that can be regarded as a thyristor without a gate. When a surge voltage exceeds the peak off-state voltage of TSS (VDRM), TSS limits the voltage below the break-over voltage. At this time, When the current flowing through TSS exceeds the switching current, the TSS will be in a short-circuit condition. When the current flowing through TSS lower than the holding current (IH), the TSS will reset to a high-impedance state.