For systems that connect to a digital transmission system it is not generally possible to break
into the line, as is done in A.2.4 for analogue lines, in order to measure the 1 kHz tone that is
demodulated by the EUT and sent to line during the testing of continuous RF disturbances.
This is especially the case for Voice over IP (VoIP) applications where the audio sent to line is
encoded into packets that may be sent for example via an Ethernet or DSL transmission
system.