This is the Solid State Logic XR622 Master Bus. It's a classic and highly reliable piece of equipment, a standard for summing mixes. It was used in a recording studio until the year before last, and then stored as a spare. However, as I no longer have an X-RACK, I haven't been able to confirm its operation. Please be aware of this. Due to the above, please consider purchasing only if you accept that returns and negative feedback regarding functionality are not possible. No claims accepted.