2 DI in a 10 mm slice
The 6ES7121-1BB00-0AA0 is a SIMATIC SC electronic submodule carrying 2 digital inputs at 24 V DC, packed 8 units per packaging unit. It occupies one slot from a possible 8 in the SC system and draws 0.4 W typical power loss. At 10 mm wide and 64 mm tall, it fits tight DIN-rail banks where every millimeter of gland-plate real estate counts. The usable terminal block is the TB 16SC.
Input characteristics and isolation
Signal "1" threshold is 13 to 30 V with a typical draw of 7 mA; signal "0" spans -3 to +5 V. Input delay from 0-to-1 ranges 1.2 ms min to 4.8 ms max, while 1-to-0 falls between 1.2 ms min and 4.8 µs max — the asymmetric response matters when the downstream PLC scan cycle expects a consistent filter window. Isolation between channels and the backplane bus is via optocoupler, tested at 1500 V AC. Between different circuits the isolation is rated 75 V DC / 60 V AC — no channel-to-channel isolation is provided, so adjacent inputs share a common reference. Supports 2-wire sensors with a permissible quiescent current up to 1.5 mA. Shielded cable runs max 1000 m; unshielded max 600 m.