Based on the same circuitry found in the Portico 5045, the Rupert Neve Designs 545 is a 500-series dynamics-taming unit, one which can be used for gating purposes in pro audio scenarios both in the studio and on the stage. It's suitable for use on both vocals and instruments and can help suppress feedback on the stage.
While it shares some similarities with conventional noise gates, the unit operates on its own principle, eschewing filtering or digital processing in favor of custom input and output transformers. These transformers help the unit sense when someone is singing or playing their instruments. When it senses signal, the unit passes signal through, and when it no longer senses signal, it reduces gain appropriately.