Beckhoff AX5721-0000 Digital encoder option card for AX51xx The AX5000 Servo Drive series supports a large number of feedback interfaces via the multi-feedback interface. Encoder option cards The AX5000 servo drives can be equipped with encoder option cards for the integration of additional feedback systems. The option cards are inserted in the second option slot on the top of the AX5000; they offer the possibility to connect one or two further encoders, depending on the version. Usually, a second high-resolution encoder offers the possibility to eliminate the backlash of a mechanism or gear unit for high-precision position control. The digital Encoder option card AX5721 provides one additional encoder input for the following feedback interfaces: EnDat 2.2 BiSS C