Circuit for testing digital lines

摘要

A digital test card for testing the quality of a digital system in a central office system is disclosed. Where the digital system consists of a digital line card connected to a customer premise equipment by a two-wire connection. The digital test card comprises a line interface which provides a full duplex transmission link. When the digital test card is testing the customer premises equipment the line interface operates as a master; when testing the digital line card the line interface operates as a slave. There is also a relay for connecting the line interface to the customer premise equipment or the digital line card. Connected between the line interface and the central office system is a buffer. A protocol controller connected to the line interface performs a packet protocol. And finally there is a processor. Under the direction of the central office system, the processor controls the operation of the digital line card and determines the quality of the digital system.