Per CISPR 22 (2005), ISN’s are specialized coupling decoupling devices used for measuring the conducted asymmetric common mode radio interference voltages of ITE. TBISN -T4 has been designed to perform conducted emissions test per CISPR 22 on two balanced p air telecom lines. It meets the requirements for Longitudinal Conversion Loss defined in CISPR 22 item 9.6.2.c)1) page 24 accepted by CISPR.