Custom-Cal also offers on-site Bit Error Rate Tester (BERT) calibration service and expedited services to meet the needs of our customers. The instruments listed below are a sample of what we calibrate and can possibly repair. Reach Technologies Inc. In addition to several standard configurations, Reach also offers custom configurations, including multi-channel and mixed data. In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit synchronization errors. These instruments generate digital test patterns, typically pseudorandom binary sequences (PRBSs), that drive devices under test (DUTs). The pattern generator sends a bit stream.