Single AC input slice for SIMATIC SC
The 6ES7121-1FA00-0AA0 is a spare-part electronic submodule for the SIMATIC SC system, carrying one digital input rated for 120/230 V AC nominal (74 to 264 V AC for signal '1', 0 to 40 V AC for signal '0'). It occupies one slot from position 8 onward in the SC backplane and draws a typical power loss of 0.6 W.
Panel fit and wiring constraints
It accepts a TB 16SC terminal block and supports unshielded cable runs up to 600 m or shielded runs up to 1 000 m.
Input characteristics and diagnostics
The input filters both rising and falling edges with a maximum delay of 30 ms — this built-in debounce prevents false triggers from contact bounce or line noise but adds latency that must be accounted for in fast-response safety logic. A green LED per channel provides a local status indication; the module has no diagnostic function or alarm output. It is compatible with 2-wire sensors, with a permissible quiescent current up to 1.5 mA (signal '0' max 2.2 mA), and draws a typical 3.7 mA at signal '1'.
Isolation and approvals
Channel-to-backplane bus isolation is provided, and the isolation is tested at 2 500 V DC. Between the M terminal internally and the inputs, the rated voltage is 240 V AC.