Einkennandi viðnám er fyrir AC-merki (eða há-tíðnimerki). Einkennandi viðnám er hugtak í langri-línusendingu. Í ferli merkjasendingar í flutningslínunni, á þeim stað þar sem merkið kemur, munu flutningslínan og viðmiðunarplanið mætast. Rafsvið myndast og vegna tilvistar rafsviðsins myndast samstundis lítill straumur og þessi litli straumur er á hverjum stað í flutningslínunni. Á sama tíma hefur merkið einnig ákveðna spennu, þannig að í ferli merkjasendingar mun hver punktur flutningslínunnar jafngilda viðnám og þessi viðnám er einkennandi viðnám flutningslínunnar sem við nefndum.
The continuity of the characteristic impedance (ρ) basically depends on the stability of the ratio of the distribution parameters L{{0}} and C0. We all know Ohm's law: U=RI, where R is the resistance or resistance load, in ohms (Ω). Resistance is related to the resistivity (also known as conductivity) of metal materials, but in the process of high-frequency signal transmission, we also need to understand the transmission of the physical medium (such as twisted pair, coaxial wire, waveguide) that transmits high-frequency signals characteristics, which are different from low-frequency signals, this transmission characteristic is related to the conductive material of the transmission medium (such as copper or silver), conductivity (resistivity), geometry (most commonly cylindrical), distributed inductance (L0), distributed capacitance (C0), insulating material (dielectric constant), etc. are all related, but the influence of these distribution parameters and the dielectric constant of insulating material is often not considered during low-frequency signal transmission.
