The characteristic impedance of a cable is simply the sum of all restrictions created by resistance, capacitance, and inductance. Impedance represents the total opposition to the flow of digital pulses. Impedance is expressed in ohms (indicated by the Greek character omega (Ω)) and, unlike R, C or L is independent of length. A low impedance is not necessarily better than a high impedance, or vice versa. The important fact to remember is that the transmitter (or driver), cable, and receiver impedances should all be the same or as close as possible.