This report provides insight and guidance on the use of a constellation of test signals covered by industry agreements on performing acceptance and maintenance testing of DS1 circuits. Information is also included on an increasingly popular signal that may be a candidate for inclusion in future industry agreements. Appendix A provides hexadecimal notation of the described test signals to facilitate their use in test equipment requiring hexadecimal input. Background material on other test signals@ and other test objectives can be found in Appendix B to this report.