The Siemens 5SY1701-2 is a SENTRON device protection switch — a 1-pole circuit breaker with an integrated auxiliary switch (normally-open contact). It carries the F1 tripping characteristic, rated 1 A at 230 V AC (50/60 Hz) and 60 V DC, with an interrupting capacity of 3 kA AC per IEC 60934. That F1 curve is a fast-acting, high-sensitivity trip designed for semiconductor and sensitive electronic loads where a standard B or C curve would let through too much energy before opening.
Snaps onto DIN rail (35 mm) — one modular width unit at 18 mm wide, so it takes up a single slot in the enclosure. Mounts horizontal or vertical; no derating penalty for orientation. The IP20 finger-safe terminals accept the usual panel wiring, and the auxiliary switch (1P+AS) gives you a remote status signal without needing a separate aux block.
Vibration-resistant per IEC 60068-2-6, so it holds up on machine-mounted subpanels. The sealable option (tamper-evident cover) is useful for installations requiring lockout or inspection seals.