The Siemens 5SY1701-4 is a SENTRON device protection switch — one pole with an integrated auxiliary switch (1P+AS), rated 1 A at AC and 60 V at DC. The F2 tripping characteristic means it's designed for short-circuit and overload protection of control circuits, solenoids, and contactor coils where inrush isn't extreme but a fast trip on a hard fault is wanted. It's built to IEC / DIN EN 60934 and UL1077, so it qualifies as a supplementary protector in UL panels.
Width is 18 mm — one modular unit — so it takes a single slot on the DIN rail. That's a standard compact footprint; it leaves room for gland plates and wire bending space in a shallow enclosure. Mounting position can be horizontal or vertical, and the supply cord can enter from any side, which helps when you're routing bundles in a crowded panel.
The 1 A rating is at reference temperature. At 35 °C it's 0.97 A, at 40 °C it's 0.92 A, at 45 °C it's 0.89 A, at 50 °C it's 0.86 A, at 55 °C it's 0.84 A, and at 60 °C it's 0.81 A.
Certified to IEC / DIN EN 60934 (equipment circuit breaker standard) and UL1077 (supplementary protector). That dual footprint means it's accepted in both IEC and North American panels as a branch-circuit supplementary protector. Halogen-free and silicon-free construction, IP20 finger-safe terminals. Vibration resistance per IEC 60068-2-6 is confirmed.