BaseUnit with AC infeed and F-DI loop-through
The Siemens 3RK1908-0AP00-0HP0 is a SIMATIC BaseUnit designed for safety-related applications, integrating AC infeed and F-DI (fail-safe digital input) loop-through in a single DIN-rail mountable package. It accepts a 24 V DC supply (20.4 to 28.8 V) and is rated for a maximum ampacity of 7 A, making it suitable for powering downstream safety modules and looping the sensor supply through multiple bases without extra wiring.
What the ratings mean for your panel
The 7 A ampacity limit governs how many safety I/O modules you can daisy-chain from one infeed — exceed it and you risk voltage drop or thermal trip on the base. The 24 V DC supply tolerance (20.4–28.8 V) covers standard industrial power rails; no separate voltage regulator needed. Spring-loaded push-in terminals accept 0.5–2.5 mm² solid or 18–10 AWG stranded, so you land field wiring without screw torque or ferrule crimping. The 6 kV surge voltage rating means the base can withstand transient spikes common on long cable runs without damaging the backplane electronics.
Mechanical integration
Snaps onto a 35 mm DIN rail and occupies 30 mm width × 215 mm height × 75 mm depth. Mount vertically or horizontally. Ambient operating range is -25 to +60 °C with derating above 40 °C; storage and transport tolerance extends to -40 to +70 °C. Shock rated at 6g / 11 ms and vibration at 2g up to 500 Hz — fine for machine-mounted enclosures near conveyors or presses. Pollution degree 2 covers typical industrial control rooms with non-conductive dust.