What it is and where it fits
The Siemens 3RK1911-1AK22 is a SIRIUS ECOFAST PROFIBUS signal refresher — a fieldbus repeater that regenerates the PROFIBUS signal on long cable runs or through IP65 junction boxes. It sits between the controller and remote I/O or drives in a distributed automation cell, with two M12 sockets on the front for the fieldbus trunk and an internal D-SUB 9-pole socket for a programming or diagnostic connection. The housing is rated IP65, so it mounts directly on the machine frame or in a washdown zone without an extra enclosure.
Signal refresher function and auto-baud
The 3RK1911-1AK22 is an active signal refresher, not a passive junction — it re-times and amplifies the PROFIBUS signal, extending the segment length beyond the standard 100 m for copper. Automatic baud rate search means it adapts to whatever speed the master sets (up to 12 Mbit/s), so no DIP-switch configuration is needed at commissioning. The internal D-SUB 9-pole socket gives a local programming port for a handheld PG or laptop without breaking the IP65 seal.
Connector layout and panel integration
Two M12 sockets (socket/socket) on the front handle the PROFIBUS trunk in and out — standard 5-pin B-coded for PROFIBUS. The D-SUB 9-pole socket is inside the housing, accessed by opening the cover. IP65 on the front means the M12 connectors are sealed when mated; the backplane or mounting surface must provide the rear seal. Mounts via the two fixing holes in the base — no DIN rail required, so it bolts to a machine frame or a sub-panel gland plate.