Amendment 1 to Recommendation ITU-T K.21 refers to Annex A. Annex A applies to special environments, one factor being that the primary protection has a poor earth connection that does not meet the requirements of Recommendation ITU-T K.66. This condition is simulated by increasing the STP earth resistance (R1) from zero to 100. People have missed this change, possibly because the test circuit diagram is in Recommendation ITU-T K.44. To alert readers of this a text note has been inserted in the Comments column.