The Siemens 3RK1901-1MX01 is an AS-Interface Extension Plug Plus — a powered repeater that doubles the cable run to 200 m per AS-i segment while embedding an A/B slave for line diagnostics. It draws 15 mA from the AS-i bus (26.5–31.6 V) and is rated IP67, so it lives directly on the machine frame or in a washdown zone without an enclosure. The integrated slave reports undervoltage conditions on two inputs: IN3 flags a drop longer than 50 ms, IN4 catches anything over 5 ms — useful for tracing intermittent supply dips on a long bus.
Deployment context
The Extension Plug Plus connects via an AS-Interface M12 feeder (3RX9801-0AA00, ordered separately) and sits inline on the AS-i yellow cable. IP67 lets it mount directly on a conveyor frame or robot cell without a panel — the housing and connectors handle washdown. The integrated slave means you get diagnostic data (undervoltage, communication health) back through the AS-i master without a separate gateway.
I/O configuration and diagnostics
Configured as an A/B slave with I/O configuration B. OUT1 (D0) is not required; OUT2 (D1) sets the switching threshold — 26.5 V or 23 V, selected by the slave's parameterization bit. IN3 (D2) reports undervoltage > 50 ms; IN4 (D3) reports undervoltage > 5 ms. The polarity reversal protection is built in.