Ok, it's clear to me that waveguides are for sending EM waves from one place to another (e.g. TEM, TE, TM modes). But what about TLs? I've seen them described as carrying AC signals (V or I) but also EM waves, e.g. TEM waves in coax cable. What gives? Does one imply the existence of the other? When the coax cable's signal enters my TV, what is the "data" - the V/I waveform or the EM waveform?