Built-in self-test is a functional requirement that a complex electronic system must satisfy in order to provide efficient production testing and system maintenance. Effective solutions with minimum possible hardware overhead are needed. With the advent of application-specific integrated circuits, integration of functions conventionally performed by external instrumentation in a single test IC on a board has become a reality. The paper gives an example of how advantage of user programmable logic was taken in the design of built-in self-test for telecommunications equipment.