over voltage protection
TVS -- transient voltage suppression
Transil -- TVS diode
1 picosecond activation time -- inductive effects are slower and will be over greater concern at these speeds.
When triggered, the Transil absorbs all excess energy above the breakdown. This sets limits to what it can handle before failure. Failure may be open circuit, which means that it also fails in its protection to the rest of the circuit.
Trisil -- thyristor surge protection device
Used as a crowbar trigger, so all excess energy is not absorbed by the device itself (unlike a Transil TVS diode).
Similar to a SIDAC, but intended specifically for high voltage and high power surge protection.