This addendum provides changes to TSB-31-D, Telecommunications – Telephone Terminal Equipment – Rationale and Measurement Guidelines for U.S. Network Protection. Changes in this addendum include:

- additions to the references in Clause 3

- addition of some definitions

– Subclause 4 Definitions, Acronyms and Abbreviations;

- modifications to the test sequence

– Subclause 6.1 Sequence of Environmental Simulations;

- modifications to grounding requirements when performing longitudinal voltage measurements

– Subclause 9.15 Non-LADC Longitudinal Voltage – 0.1- 4 kHz and subclause 9.17 Non-LADC Longitudinal Voltage – 4 kHz to 6 MHz; and

- new subsection on test procedures for performing out-of-band metallic and longitudinal noise measurements on equipment with acoustic inputs - Subsection 9.41 Acoustic Stimulus For Performing Measurements On Acoustically Coupled Devices.

The other clauses and subclauses in TSB-31-D are not affected. Additions to the text are shown underlined and deletions are shown using Words that appear in underlined italics are intended as instructions to the reader.