Traditional types of line testing equipment were not designed to meet the requirements of this new paradigm. It is not surprising, then, that traditional types of test equipment are unable to monitor a wide range of parameters and provide the quality and range of tests now required.

The shortcomings of traditional line testing devices affect many aspects of a company's operations. For example, many do not provide accurate tests of trouble spots. These trouble spots often occur in the copper subscriber loops and in electronic switching and transmission elements that use these loops to provide dial tone and other services. Without accurate information, a maintenance supervisor is forced to guess at the nature of a trouble as well as the type of equipment and technician experience level needed to repair it. The maintenance supervisor could easily dispatch the wrong technician and equipment for the job—a costly and time-consuming mistake. With inaccurate testing, a technician might even be dispatched to a site that needs no repair or is "found okay out."

Traditional test equipment suffers from other disadvantages. Such devices are not equipped to provide the information needed to prequalify lines for increasingly popular digital services such as integrated services digital network (ISDN) and digital subscriber line (xDSL). Also, as a result of the limited information many of the traditional line testing devices provide, it cannot be integrated into company-wide databases or used effectively throughout an organization.

Another Testing Challenge: Deregulation

With the deregulation of services, the shortcomings of many traditional test devices have become even more obvious. Service providers are under increased pressure to maintain a higher level of service in order to retain the loyalty of their customers. Because traditional testing devices are unable to access the unbundled local loop adequately—the most critical point in assessing network problems—these devices cannot provide the type of information needed to maintain telco infrastructure properly.

Current Test Strategies

Today, four basic techniques are employed to carry out line testing. The three traditional methods are copper bypass pairs, digitized bypass pairs, and line testing equipment that is built into switches and digital loop carriers (DLCs). An increasing number of telcos are relying on a fourth method: a stand-alone line test system. In the following sections, the tutorial evaluates the ability of these methods to to accommodate the demands of the new testing requirements and explains how each of these methods works.