Its 8.55V reverse standoff voltage means it stays off below that level, then avalanches at a minimum of 9.5V to shunt the surge. With a peak pulse power rating of 1500W and a clamping voltage of 14.5V maximum, it protects downstream circuitry from lightning-induced transients, inductive load switching, and ESD events in general-purpose industrial and telecom equipment. The DO-201AD axial package is through-hole mountable, making it a straightforward replacement on legacy boards.
The 103A peak pulse current at that waveform tells you the part can handle a heavy surge, but the clamping voltage of 14.5V is the number that matters for the protected device: if your load can't survive 14.5V, you need a lower-clamp part.
Sourcing reality: obsolete status and what to do
The 1.5KE10AG is marked obsolete by onsemi. The base product number 1.5KE covers a family of voltage variants; a pin-compatible alternative within the same 1.5KE family (e.g., 1.5KE10A) may be available if the 'G' suffix (lead-free / RoHS) is not a hard requirement. We can source the part against an RFQ — confirm your quantity and we'll check open-market availability.