What it is and what it fits
The Siemens 6ES7403-1JA00-0AA0 is a SIMATIC S7-400 ER2 expansion rack with 9 slots, designed exclusively for signal modules — no CPU or power supply slot on this backplane. It extends the I/O capacity of an S7-400 system by housing up to nine signal modules (digital/analog input or output) in a separate chassis, connected via the rack bus to the central controller.
Integration note
Mounts in a standard 19-inch cabinet or panel; the rack connects to the S7-400 central controller via the backplane bus cable (not included). No DIN-rail clip — it bolts into the enclosure. Only signal modules populate these slots; the CPU and power supply reside in the central rack (UR1/UR2). Verify bus cable length and slot numbering before commissioning.