Dear friend!
It acts as a gauge.
The pseudo random binary sequence (PRBS) functional module is equivalent to a simple instrument that transmits and receives unframed services independently. An NE that provides the PRBS function can be used as a simple instrument to analyze whether a service path is faulty. By using the PRBS function, you can analyze the local NE and the entire network. Therefore, you can perform a test without using a real instrument during the deployment or fault locating.
More: How to test the availability of E1 services
Thank you!