We have received a number of questions about this test parameter. It is important to note that this is not a field test requirement. However, it is a component requirement. The connecting hardware and cable vendors have to meet the TCL requirement. The assumption is that the sum of the components will not exceed XX dB. And that’s because until the recent announcement of the DSX-5000 CableAnalyzer, no field tester could do this measurement. The DSX-5000 CableAnalyzer can perform field meaurements for TCL and ELTCTL.
From ANSI/TIA-568-C.2
6.2.14 TCL Channel TCL shall meet or exceed the values determined using the equations shown in Table 16 for all specified frequencies. Calculations that result in category 6A channel TCL values greater than 40 dB shall revert to a requirement of 40 dB minimum. Compliance to these requirements is intended to be verified by laboratory measurements.
6.3.14 TCL TCL is not specified for permanent links.