The Siemens 3RK1901-1MX00 is an AS-Interface Extension Plug — a passive bus component that extends the reach of an AS-i segment. It carries no slave logic itself, so it doesn't add nodes to the network; it just pushes the physical layer out another 100 m, doubling the standard segment to 200 m total. That's the whole job: more cable length, no extra addressing. It's IP67-rated, meaning the housing and the M12 connection point handle washdown environments — food processing, automotive paint lines, any spot where a standard IP20 bus repeater would get hosed down and fail. Supply voltage comes straight from the AS-Interface bus (26.5 to 31.6 V per the AS-i spec), and the plug draws only 10 mA — negligible load on the AS-i power supply. A green LED on the supply voltage line confirms the bus is live; a flashing LED between 10 and 26.5 V warns of a brownout condition.
Pinout and Connection — What You Need to Wire
Pin 1 is U AS-Interface +, Pin 3 is U AS-Interface -. That's the standard M12 pinout for AS-i power and data on the same pair. Polarity reversal protection is built in, so a swapped pair won't fry the plug — it just won't light up until you correct it. The plug connects via an AS-Interface M12 feeder, order code 3RX9801-0AA00, which must be ordered separately. That feeder is the physical tee that drops the extension cable off the main trunk. No feeder, no connection — it's not included in the box.