Secondary Line Protection for T1 and E1 Line Cards

The lower cost of high speed digital T1 and E1 trunk lines has resulted in the increasing deployment of this technology in place of traditional analog lines. In the past, T1/E1 trunks were used primarily in protected telephone company central office transmission applications, but now they are used outside the central office to bring higher capacity service directly to customers. The broader application of this technology makes it important for line card designers to include secondary protection circuitry in their designs.