The Cable Chronicles: The History of Ribbon Cable

Cable-ChroniclesIf you’ve ever peeked inside the workings of your computer, you’ve likely seen a ribbon cable or two, connecting your hard drive and other storage drives to the motherboard. Ribbon cable has been a staple in the data communications industry for decades, but like all enduring computer components, the ribbon cable has had to evolve to avoid becoming obsolete in the digital era.  

As you might guess, ribbon cable got its whimsical name from its design—a wide, flat molded construction featuring many conducting wires running parallel to each other. Because the conductors lie in the same plane, the product is also sometimes called multi-wire planar cable, or simply flat cable.

Types of Ribbon Cable

Ribbon Cable

Invented in 1956 by the Cicoil Corporation, the ribbon cable’s flat design was engineered to replace large, awkward and inflexible round cables in computer systems. They were first put to work in mainframe computer devices like card readers and punching machines. By the 1960s, NASA was using ribbon cable in milestone aerospace applications, like the first lunar landing.

Ribbon cable’s speedy rise to popularity can be attributed, in large part, to its convenience. Because the cable lies flat, it takes up little room and can even be run under carpeting. The design also lends itself to easy mass termination with Insulation Displacement Connectors (IDC).

Growing competition between flat cable manufacturers created a push for standardization that would achieve higher quality, easier installation and lower costs across the board. Ribbon cables are called out by the number of conductors, often termed “ways,” and the spacing between them, known as “pitch.” While they can still be made in all sizes and variations, the most common pitch is 0.050 inches. Common conductor counts range from 4 to 80 conductors. A standard flat cable, like a gray PVC ribbon cable, is often marked with a red polarity stripe along one edge that indicates which conductor should be matched to Pin 1 on the connector. This prevents component damage by discouraging reverse connections. Some applications benefit from a “rainbow” ribbon cable, which identifies each conductor with a different color.

For some time, ribbon cable was used for both internal and external computer connections in computers like the Apple II. However, some of the same characteristics that make flat cable ideal for tight spaces inside computers make it less suited to connecting outside devices.  The wide flat shape that makes ribbon cable so convenient in some places can also impede computer cooling by blocking airflow. In addition to that, the construction offers no sideways flex and can make a cable bunch unmanageably awkward.

In the 1980s, the FCC discovered an unintended quality to ribbon cable—it made an excellent antenna, and broadcasted signals that interfered with analog TV reception.  A variety of workarounds were developed, but the stand-out solution was the round-to-flat ribbon cable. In a round-to-flat cable, a ribbon cable is twisted into a round shape before being taped, but left flat at the ends so that it can still be terminated with IDC connectors. It offers the best of both worlds. While flat ribbon cable has remained popular for internal computer wiring, round cables have replaced flat data cables in external connections.

As so often happens in the wire and cable industry, the differing cable constructions and standards converged and became compatible but left behind a variety of names to confuse wire buyers. In addition to “flat cable” and “multi-wire planar cable”, ribbon cable can also be called out as ATA cable, because it falls under the ATA (Advanced Technology Attachment) interface standard. You may also see it called PATA (Parallel ATA) cable, a name developed to differentiate from the more recent and smaller SATA (Serial ATA) cable. The ATA interface evolved out of the IDE (Integrated Drive Electronics) interface, so it is not uncommon to see ribbon cable referred to as IDE cable.

Today, ribbon cable comes in all different shapes, sizes and colors, and can be referred to by many names. It can be used in a huge range of applications, from high speed computer connections with coaxial ribbon cable to rainbow ribbon cable in Ghostbusters’ proton packs!

Still have more questions? Check out our Ribbon Cable FAQ page or browse our large selection of commercial and mil spec ribbon cable to see more details.

The Cable Chronicles: The History of Wind Energy and Wind Cable Standards

Cable-ChroniclesIn the last Cable Chronicles article, we talked about the history of solar power as a renewable energy source and the progression of solar cable standards. This time we’re going to breeze through another green energy source with a long history—wind power! And we’ll take a look at the wind cable standards that have come along with it. 

There are records of humans harnessing wind energy to propel their boats as early as 5000 B.C. Windmills got their start pumping water and grinding grain by 200 B.C.  But even electricity-producing windmills have been around for some time, the first ones popping up in Denmark in the late 1800s. Wind turbine cable standards, on the other hand, have seen most of their development over the past decade.

Wind Turbine Cutaway

Inside a Wind Turbine

Not too long ago, there was no such thing as a dedicated “wind turbine cable.” Wind turbine designs called for other common cables, like welding cable, DLO cable, SOOW and SJOOW portable cord, XHHW cable and RHH/RHW cable, etc. But wind applications demanded more than these products could provide.

Wind developers began to engineer wind turbine cables with qualities that enhance efficiency and longevity: strong torsional and bending flexibility and resistance to electromagnetic interference, high winds, extreme temperatures, UV light, chemicals, oils, and even salt spray in some applications. Now we have all kinds of wind farm cable available from many manufacturers. Instead of using TC-ER cable rated to only 600 volts, wind farmers can use WTTC rated cable, good to 1000 volts. There are wind turbine cables with various flex levels: Standard, Premium and MegaFlex. You can also get WTTC rated Servo cable and VFD cable, designed to withstand the particular challenges of the wind power industry.

With new wind cable products on the market, new standards became increasingly necessary. For some time, one of the only wind turbine component-specific ratings out there was UL 2277 for Wind Turbine Tray Cable (WTTC Cable). Many other common cables used in wind turbines, like those listed above, have been subject only to the generic provisions of the NEC. A few regulations pertinent to wind turbine systems were lumped in with Article 705 of the NEC, a section mostly applicable to photovoltaic systems.

In the 2011 version, the NEC added Article 694, which pertained mostly to small wind turbine systems.  The 2014 version expanded the section to include large systems as well. The UL covers Wind Turbine Generating Systems (WTGS), smaller Wind Turbines (WT) and their components under UL 6140, 6141, 6142 and 6171.

These standards will continue to evolve rapidly as new components and methods are adopted. For example, in the last few years, there has been some experimentation with fiber optic cables in almost all components of a wind turbine generation system. If that takes off, maybe we’ll see something addressing it more specifically in the 2017 NEC! Until then, you can learn more about WTTC rated wind cables here.

The Cable Chronicles: History of Solar Power and Solar Cable Standards

Cable ChroniclesHumans have been harnessing renewable energy sources, like solar power, longer than most people realize. As early as 7th century BC, people were intensifying the rays of the sun with the help of a magnifying glass to build fire. In modern times, solar energy is harnessed on a much larger scale and there is an extensive history behind the technological advances that have brought us to the solar cells we use today. Although standards for the solar wire used in these applications are relatively new, they have already seen quite a progression of their own.

Before we could make it to solar cable and solar cable standards, we needed to work our way up to modern solar technology – the technology we’d need to harness electrical power via the sun’s rays.

In 1839, French scientist Edmond Becquerel discovered the photovoltaic effect: the creation of voltage or electric current in a material upon exposure to light. For the next century or so, scientists tinkered with the concept and photosensitive materials like selenium, but in 1908, William J. Bailey of the Carnegie Steel Company invented a solar collector with copper coils and an insulated box, which was essentially a blueprint for the modern solar cell. By 1950, three engineers at Bell Telephone Laboratories created the first solar cell powerful enough to convert the energy needed to run standard electrical. Since then, scientists have continued to work to improve the conversion rate, equipping us to power special cars, aircrafts and even entire buildings with the use of modern solar arrays.

For a long time, THHN wire was used as solar power cable in these arrays. THHN is “Thermoplastic High Heat-resistant Nylon-coated” general purpose building wire. It is used in a wide range of industries and applications, and its heat resistant properties made it more suitable for solar applications than other types of wire and cable. It was a sensible choice for use in evolving solar technologies. Historically, UF, SE and USE wire were also used in various components and were covered in sections of the National Electrical Code dealing with photovoltaic systems.

As of the 2008 version, the NEC only lists PV Wire and USE-2 Solar Wire (commonly dual-rated as RHH/RHW-2 wire) as acceptable options. They are safer, sturdier and more efficient than their predecessors.

PV Wire

PV Wire

PV wire meets current UL standard, UL 4703. Photovoltaic wire is rated to 90°C in wet and 150°C in dry conditions, and to 600, 1000, or 2000 volts. It is known for its use as underground service entrance cable and can be used in either grounded or ungrounded arrays. It is often used in exposed applications and has thicker insulation and jacketing, better sunlight resistance, flame resistance, and flexibility at low temperatures than USE-2 cables.


USE-2 Wire

USE-2 Wire

USE-2 cable is regulated by the UL 854 standard. According to UL experts, it is popularly chosen for underground applications, although it is also appropriate for exposed use according to Sec. 690.31 (B) of the NEC. It is rated to 90°C in wet and dry conditions, and to 600 volts. USE-2 wire is more crush and impact resistant than PV wire.


Although USE-2 and PV wires have been developed specifically for modern solar power cable applications, it isn’t to say that other wire types have completely outlived their usefulness in the solar industry. Wires like THHN can still be used in certain PV functions where it is safe to do so. However, it should never be used to replace PV or USE-2 wire where they are specified, as it does not include all of the specialized features incorporated into PV wire and USE-2 wires, and could lead to failures.

The history of solar power and solar power cable is rich, despite the relatively short time cabling standards like those for USE-2 wire and photovoltaic wire have had to develop. As we continue to refine solar energy processes and the materials we use in building the arrays, it is almost certain that our standards will also continue to evolve.

To learn more about the current uses of popular solar cables, watch our PV Wire vs. USE-2 Wire video.

Introducing the Cable Chronicles Series!

Cable ChroniclesCurious to know how a new cable standard came about or why a certain cable is built with a particular material? Our new “Cable Chronicles” series on the AWC blog aims to answer those burning questions. We’ll give you a peek into the history of your wire and cable and how it made its way to modern day. Whether we’re looking at the evolution of standards or changes in the products themselves, these interesting articles are sure to give you a better understanding of the wire and cable you work with today, and maybe even a perspective on its relevancy in the future.

Stay tuned for the first installment coming next week! If you can’t wait for the learning to begin, feel free to browse our Allied Encyclopedia articles in the meantime.

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