The Siemens 6ES7921-4BC50-0AA1 is a pre-assembled front connector for SIMATIC S7-400 digital I/O modules. It comes with four round cables, each 2.5 m long, terminated with screw-type terminals on the field side. The 48-pole connector mates directly to the S7-400 front interface, so no field wiring to the module itself is needed — you land your field wires on the screw terminals, then plug the assembly onto the module.
Rated at 60 V DC and 1 A per contact, with a total current limit of 4 A across all 48 poles. That 1 A per contact is the continuous current each signal path can carry — fine for 24 V DC digital inputs and outputs typical in S7-400 racks. The 4 A total means you cannot load all 48 contacts at 1 A simultaneously; the aggregate is the limit.
Installation note
Mounts directly onto the S7-400 module — no DIN rail or additional bracket. The cable exits at the top, so plan for overhead clearance in the cabinet. The 2.5 m cable length is the distance from the connector body to the terminal module; it is fixed, not field-cuttable. Screw-type terminals accept 0.14 mm² round cable as supplied; field wiring should use ferruled stranded conductors matching the terminal block specs.