What this 16 A, Curve D, 4-pole MCB does in a panel
The S204-D16 is a 4-pole miniature circuit breaker rated 16 A with a Trip Curve D characteristic, meaning it's designed to handle high inrush currents typical of motor, transformer, or power-supply loads without nuisance tripping — the magnetic trip operates at 10 to 20 times the rated current, so it rides through the startup surge of a 16 A motor load that a Curve B or C breaker would trip on. Rated 277 VAC with 10 kA interrupting capacity. 4-pole breaker isolates three phases plus neutral in one DIN-rail footprint. Mounts on standard DIN rail with finger-safe terminals. 4-pole form factor occupies four modular units on the rail.
Listed under UL 1077 (Supplementary Protector) and CSA 22.2 No. 235, which means it's recognized for use within an equipment assembly where an upstream branch-circuit overcurrent device already provides fault protection — not a service-entrance or main breaker, but a supplementary protector for a specific load branch inside the panel.