The Siemens 6ES7963-3AA00-0AA0 is a SIMATIC S7-400 Interface Module IF963-X27 — a replacement part for point-to-point (PTP) coupling with the CP441 communications processor. It provides an RS422/RS485 physical layer interface for the S7-400 backplane, rated for a maximum transmission rate of 115.2 kbit/s. Cable length reaches 1 200 m at 19 200 bps.
The 115.2 kbit/s maximum transmission rate is the ceiling for this RS422/RS485 interface. If your CP441 PTP link runs at 19 200 bps, the cable length can go the full 1 200 m. Push it to the max rate and the reliable distance drops — the cable length spec is conditional on the baud rate. Current consumption of 250 mA and power loss of 1.25 W are modest for an S7-400 backplane slot.