If the cable is terminated with the equivalent resistance of the characteristic impedance of the cable, you can not distinguish the cable from the source whether it is infinite - all the signals fed into the cable are absorbed by the cable and the load.

If the impedance does not match, some of the waves in the cable will be reflected from the cable mismatch, and when these reflected waves collide with the signal generator (source), they are reflected again and are mixed with the normal signal being transmitted, Which is the original signal, which is again reflected wave.

The same is true when the signal pulse is sent out of the cable - some energy is reflected back to the source when an impedance that does not match the impedance characteristic of the cable is encountered. If the signal pulse reaches the open or shorted end of the cable, all the energy is reflected back (except for the attenuation loss part - this is another topic). If the other does not match the termination of the situation, then some energy will be reflected.

The reflected energy will distort the signal, and if the impedance of the signal generator and the impedance of the cable are different, the energy will be reflected again to the cable terminal, forming an excess pulse signal.

The above is a brief introduction to the characteristic impedance of the data transmission. For more information on the characteristic impedance, please pay attention to the kingsignal official website.