The characteristic that is most important characteristic of any transmission line is its characteristic impedance, Z0. CI(characteristic Impedance) is defined as the ratio between the voltage and current
Characteristic Impedance Ratio = (v/i),
at the input of a line of infinite length. If the impedance value of the signal source is equal to Z0, all of the power that is generated by the source is transferred to the line. Opposing to this, if there is an impedance level Z0 at the far end point of the line, all the power of the signal shall be transferred to this. It implies that a lossless line transfers all the power from a source to the receiver.
But, to make it happen, the source and receiver impedances must be at equal level (matched) to the line impedance. If the impedance level at the far end of line is not equal to Z0 (including event when it is an open circuit, or when there is a short circuit) part of or all of the energy of the signal is reflected back along the line. This makes the standing waves to form in the conductors, and only very few power is transferred to the receiver. For having quick transmission of signals, this should be avoided by careful matching of impedances.
