What Every Purchaser Needs to Know About Sourcing Wire & Cable: Your Guide to Wire & Cable Procurement

Moving Electricity From Point A to B:

Power Versus Signal

For the world of wire and cable, this has tremendous implications about how the cable will be used and how it must be designed. An electrical pulse can travel great distances, even running through complex switching systems without diminishing too much. And it can do so at low voltages, which are safe and cheap. It means that first the telegraph, and later the telephone, operated effectively and inexpensively over great distances, transforming our world. And it led, eventually, to microprocessors that also communicate in a binary system — pulses strung together.


OK, so what how does this affect cable? Again, power and signal.


Power cable is designed to carry as much power as needed to run the machine. A toaster needs 10 amps (in 120 volt systems), so 18 AWG works fine. A welder needs 75 amps, so 4 AWG works fine. A steel-cutting machine needs 500 amps, so the conductor is much bigger. The critical factors involved in selecting power cables include amp draw, temperature required (both inside the conductor and ambient), insulation type specific to the application, and many others particular to the situation.


Signal cables, on the other hand, are mostly concerned about how to move the pulses down the conductor fast, and how to make sure they stay true and do not get distorted — distorted by small imperfections in the conductor, distorted by other conductors nearby, or distorted by a whole host of other factors. Signal cables, which are generally (but not always) used in low voltage applications, are concerned only with moving those pulses. Design features include the need for shielding, twisting requirements, insulation types, and many other details specific to the application.


A talented telegraph operator could provide about 4 pulses per second.¹ A good data cable, Cat 6 for example, can provide about 600 million pulses per second (600 MB at 250 MHz).² And fiber optic cables, which transmit light through glass even faster than

electricity through copper, are super high-speed. But that’s a topic for another day. 


If you remember power versus signal, making something go versus sending a pulse, all other considerations about cable selection get easier.


¹The Telegraph: A History of Morse’s Invention and Its Predecessors, Lewis Coe, 2003. P. 126.

²CompTIA Network+ 2009 In Depth, Tamara Dean, 2009. P. 104.

If you’re in the cable industry, it’s useful to learn the difference between electrical power and signal.

  • Electrical power makes things “go”
  • An electrical signal is a pulse — a blip — that does not make things “go”

First, the easy one — electrical power. Plug in your toaster, push the lever down: the power flows to the toaster and through the coils, heating them up thereby making your bread a lovely golden brown. Pushing the lever closed a switch, and the electricity was able to flow out of your wall, much like opening a dam allows water to flow down a spillway. The electric company is generating power, just like rainwater filling a reservoir, and closing the switch merely allows the electric power to run through your toaster. The same concept explains your lights at home, a welder joining two pieces of metal, or a steel-cutting machine in a factory.


Second, the more difficult one — electrical signal. The telegraph used in the mid-1800’s was the first practical use of electrical signals in industry. A telegraph operator in one location would press the hammer down onto the switch closing the electrical circuit for just a moment. The short burst of electricity moved down the conductor, sometimes hundreds of miles, and (through electro-magnetism) pulled the hammer down on the other end of the line. By stringing enough of these bursts, or pulses, together in a coordinated fashion such as Morse Code with dots and dashes, you could communicate about how much you like toast. The important point is that electricity was used, and is still used, this way simply to move a pulse down a conductor — not to power an engine or device.

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Download this entire e-book in one convenient PDF:

What Every Purchaser Needs to Know About Sourcing Wire & Cable

Download the entire e-book in one convenient PDF.

Your information will be used to send you the presentation and subscribe you to the IEWC Network. You may unsubscribe at any time.

IEWC is committed to protecting your personal information and will not share your information with third parties. For more information, please see our Privacy Policy.

Your Guide to Wire & Cable Procurement

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