For any digital communications link, the ultimate measure of its physical layer performance is whether the bits sent are received correctly. Bit Error Rate (or Ratio, as it is more correctly called) measures this performance, and BERTs are a common feature in many test labs either as BER measuring devices, or as test pattern sources for other measurements.The two most common classes are: High Speed BERTs, typically used in design and manufacturing of high-speed components and the early phases of design of boards and systems.
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