Note 1: Not applied to equipment designs to be always used with primary protection. K.20 and K.21 equipment also need operator agreement.
Note 2: Equipment containing high-current-carrying components that eliminate the need for primary protection shall be tested without primary protection. Equipment shall use special worst-case high-current-carrying components.
Note 3: To suit local conditions, a voltage of 300 V rms 3⁄4 V 3⁄4 600 V rms and time t 3⁄4 1.0 sec may be specified. The series current limit resistance shall then be R = V(t).0.5
Note 4: All voltage-time combinations shall be tested as defined by the time equation.
Note 5: Equipment that is always used with primary protection shall be tested with a special agreed primary protector.
Note 6: Apply K.45 port-to-external port test at the K.20 enhanced level for small telecommunication centers with fewer than 250 lines.