forward-conducting diode thyristor surge protective device

A two-terminal internally triggered thyristor surge protective device that switches only for negative terminal-2 (cathode) voltage and conducts large currents at positive terminal-2 (cathode) voltages comparable in magnitude to the on‑state voltage.

NOTE 1 In conventional thyristor terminology, this device would be called a reverse-conducting diode thyristor.

NOTE 2 When terminal 2 (cathode) is positive, the device characteristics are similar to those of a forward-biased diode.

NOTE 3 When terminal 2 (cathode) is negative, the device characteristics are similar to those of a breakover-triggered SCR.

References: 

JESD77-B, 2/00