BERT or bit error rate test is a testing method for that uses predetermined stress patterns consisting of a sequence of logical ones and zeros generated by a test pattern generator. A BERT typically consists of a test pattern generator and a receiver that can be set to the same pattern. They can be used in pairs, with one at either end of a transmission link, or singularly at one end with a at the remote end. BERTs are typically stand-alone specialised instruments, but can be.