The ?143-500-18 from Proton-Electrotex JSC is a Silicon Controlled Rectifier with Breakover Voltage 1800 V, Breakover Current 13.0 to 16.0 kA, Gate Trigger Voltage 1.50 to 3.00 V, Gate Trigger Current 150 to 400 mA, Temperature Operating Range -60 to 125 Degree C. Tags: Disc. More details for ?143-500-18 can be seen below.