scope:

The requirement for analog tests on digital subscriber lines is specified in OAM&P service standards. These tests are generally needed for metallic pairs assigned to digital subscriber services and transport technologies such as ISDN,HDSL,ADSL,DOV,DLC, etc. This technical report describes algorithms to determine the presence of load coils on such facilities. Once other services or transport technologies are defined and their signal formats specified, the necessary algorithms and test limits will be included in this report. This report discusses desired features for load coil detection algorithms and the technical features available with each algorithm.

Unbalance in the loop may limit the effectiveness of load coil detection algorithms. However, this report does not address these potential limitations. The effect of unbalances on these algorithms is for further study.

Note: The user's attention is called to the possibility that implementation of this Technical Report may require the use of an invention covered by patent rights.

By publication of this Technical Report, no position is taken with respect to the validity of this claim or any patent rights in conjunction therewith. The patent holders has, however, filed a statement of willingness to grant a license under these rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such a license. Details may be obtained from the publisher.

Purpose and Application

New digital services and loop transport technologies such as ISDN,HDSL,ADSL,DOV,DLC, etc. require bandwidth above the voiceband on metallic pairs. Because the bandwidth is broader than that required for voice and voiceband data services, load coils must be removed. Furthermore, tests may be required to verify their removal. These tests are particularly useful for facility qualification (when needed) and during initiation and repair of these services. Should load coils exist, the loop would probably not support the digital subscriber line (DSL) service. Various techniques for verifying existence of load coils are presented. The 2B1Q digital signal format can be assumed when specifying algorithms for basic rate ISDN. Algorithms which may be applicable for other services such as ADSL or HDSL are included in this report.