What you’re looking at
This is the Siemens LOGO! 24RCO (AC) — order code 6ED1052-2HB00-0BA3. A logic module without a display, running on 24V UC (AC or DC), packing 8 digital inputs and 4 relay outputs. The relays are rated 10 A resistive, 3 A inductive, so it’ll switch small contactors, lights, or solenoids directly. Power reserve holds the program and real-time clock for 80 hours — handy when the panel loses mains overnight.
The physically identical variant is 6ED1052-1MD00-0BA6 — same 72 mm wide (4TE) DIN-rail footprint, same I/O count, same 0 to 55 °C range. The -1MD00 adds a backlit display and four analog-capable inputs (0–10 V). If your panel was laid out for the display version, this one drops right onto the same DIN rail without rewiring. What you lose is the on-board HMI and analog channel — your PLC or HMI has to handle that elsewhere. For a budget line or a remote station where nobody reads the local display, this bare-bones variant saves a few dollars per unit.
Mounting & wiring check
No onboard short-circuit protection on the outputs — Siemens expects an external fuse per output or a common feeder fuse. The relays are free-wheeling diode protected internally? Not stated, but the inductive load rating of 3 A suggests basic suppression. If you’re switching solenoids or small contactors, add a suppression diode or RC snubber at the load to extend contact life.