The 1.5SMC120A: That 1500 W rating means it can clamp a transient up to 9.2 A peak pulse current without exceeding the 165 V clamping voltage — the energy is absorbed in the silicon junction, not passed downstream. The reverse standoff voltage is 102 V, so it sits across a 100 V or 120 V DC rail without conducting in normal operation. Breakdown occurs at 114 V minimum, and clamping is at 165 V maximum — the margin between standoff and clamp defines the protection window for the downstream circuitry.
It is a single unidirectional channel — the cathode band marks the protected line side, the anode connects to ground. No power line protection (it is not designed for AC mains clamping), so it fits DC rails, signal lines, and low-voltage power buses.