We don’t give it any thought, but cables are around us everywhere we turn. The importance of cables & connectors is certainly hidden (or buried – in the walls that is), but nonetheless, exists. Cables are everywhere we look. While we don’t actually see them, they serve us in many of our daily needs. Our homes are wired with various cables, bringing us data signal, electricity, etc. offices, hospitals, even amusement parks, are all wired with long spans of cables, allowing our routine to exist.
You would only think of cables when you need to buy one. Once in the store, you may be overwhelmed with the numerous types of cables and connectors available to choose from. Cables are typically made of one or more wires, wrapped in insulation and terminated by a metal connector on each end. So how does one choose?
There are three elements that need to be considered when looking at cables – electrons, voltage & current; shielding and impedance.
Electrons, voltage & current
Electrons move through conductors – if a wire is connected to two ends of a battery – there will be a flow electron. This movement of electrons has numerous characteristics; two of them are voltage and current. Voltage can be described as the” pressure” created by the flow of electrons. Current = the rate of the resulting flow.
Resistance is the ability of a material to restrict the free flow of electrons. Metal wires are good conductors. They have a large surface to volume ratio, which is important because electrons travel over the surface of the wire.
Electric & magnetic interference is in the air all around us. It comes from power sources that may cause noise. This noise may be picked up by cables unless they are properly shielded. A shield is a conductive material that absorbs external signals.
Audio and video signals are alternating current signals. They can be described as waves. For a wave to pass cleanly across a cable from one component to another, the impedance (signal opposition) must be equal all the way across. The cable must be rated to carry signal at certain impedance.
If the impedances do not match between signal source, cable & receiving component, the waves will get out of phase and collide with each other. This will reflect some of the signal power back to the source, causing noise and signal loss.
Making an Educated Selection
– Use cables for their application (use a video cable for video, audio cable for audio – don’t try mixing them for any reason).
– Buy the cable length you need, no longer (longer cables equal more exposure, which may translate to potential failure).
– Choose flexible cables for portable needs and rigid cables for permanent installations.