The 1.5KE56ARL4G: It clamps transients at 77V max, with a reverse standoff of 47.8V and a minimum breakdown of 53.2V. The DO-201AD axial package is through-hole mount, common on power input boards and industrial control panels where a soldered-in transient suppressor is preferred over a surface-mount part for mechanical robustness.
The 1500W peak pulse rating at 10/1000µs means this diode can absorb a 19.5A transient current before the clamping voltage rises to 77V. The operating temperature range spans -65°C to 175°C junction, so it handles the thermal extremes of outdoor enclosures or engine compartments. No power line protection is listed — this is a signal or low-voltage DC rail suppressor, not for AC mains.
Lifecycle reality — obsolete but sourceable
Littelfuse lists the 1.5KE56ARL4G as obsolete. That means new designs should look at the current 1.5KE series (same DO-201AD package, same 1500W rating) for a pin-compatible drop-in — the 1.5KE56A variant is the closest active sibling.