The Siemens 6ES7461-3AA00-0AA0 is a SIMATIC S7-400 IM461-3 receiver interface module. It handles the receiving end of a distributed connection, linking remote I/O racks or subracks back to the main S7-400 rack over the K bus at distances up to 102 m.
The 102 m maximum distance is the practical limit for the K-bus extension between the sender (IM461-1 or IM461-2) and this receiver module. Beyond that, signal integrity drops and the bus may not synchronize. In a real S7-400 rack, this module occupies one slot and draws its power from the backplane — no separate supply needed. The K bus is the local I/O bus inside the S7-400 chassis, so this module is for extending that bus to a remote subrack, not for PROFIBUS or PROFINET fieldbus links.