This addendum provides changes to TSB-31-D, Telecommunications – Telephone Terminal Equipment – Rationale and Measurement Guidelines for U.S. Network Protection and to its addendum TSB-31-D-2. Where the text of TSB-31-D-2 is modified in clause 2 it is clearly identified.

Clause 2 of this document provides the corrections to numerous clauses within TSB-31-D and TSB-31-D-2.

Clause 3 of this document provides revised text for the grounding requirements of sub-clause 9.15.8 and 9.17.8 of TSB-31-D to clarify that any metal components of a device not normally connected to ground should not come in contact with the ground plane during testing.

Clause 4 of this document provides changes to sub-clause 5.5, Suggested Equipment List (SEL) of TSB-31-D and provides changes to the following ringing-signal-related sub-clauses under Clause 11, ON HOOK IMPEDANCE LIMITATIONS of TSB-31-D:

Sub-clause 11.2, DC Current During Ringing

Sub-clause 11.3, AC Impedance During Ringing

Sub-clause 11.4, REN Calculation.

Clause 5 of this document provides completely new sub-clauses to add the test methods for assessing DSL FAST technology to TSB-31-D.

The other clauses and sub-clauses in TSB-31-D are not affected.

For the changes provided in Clause 2, 3 and 4, additions to the text are shown underlined and deletions are shown using strikeout. The completely new sub-clause text in Clause 5 is not otherwise marked. Words that appear in underlined italics are intended as instructions to the reader.