Many of my customers are confused about the various cable standards. This blog post will explain in just a little detail what each cable standard is and what is the purpose of it. But it will only deal with external cables, not the ones inside your computer.

Serial/Parallel/Centronics

These cable standards are all but obsolete, although you may still see them on some devices. Because these are old standards, the speeds on them are fixed. A parallel cable was usually used for a printer and scanner. Quite often, the printer end of a parallel cable had what was called a centronics adapter. It was just a special connector for printers. Scanners would have two parallel ports, one for the computer and one for the printer. Serial cables were usually reserved for everything else, such as external modems.

There are two ways to transmit data: in order on the same wire or at the same time across several wires. Serial cables send all the data in order on the same wire. Parallel cables transmit the data at the same time on different wires. With the old parallel connector, this was 8 cables for data. You might be thinking it is faster to send the data at the same time across several wires is faster, but as the speed increases it is not. This is because to send the data across several wires you have to very precise timing. All the wires have to be timed just right otherwise the data is corrupted. If one wire is just a fraction of a microsecond slow, the data is no good. Furthermore, more wires mean bigger cables. For these reasons, all modern data cables are serial.

IEEE 1394 or FireWire

This standard is all but obsolete. At one time, it was faster than the USB standard. But it suffered a serious limitation in that you could not daisy chain cables through a hub like USB. The FCC required cable boxes to have a working FireWire outlet, but cable companies barely supported it so it was an ineffective way of transferring recorded programs from your DVR to your computer. There are two versions of the cable, a regular sized connector and a mini connector. The IEEE organization defined the standards for FireWire, much like they do for networks and many other standards. FireWire is just a friendly name for the IEEE 1394 standard.

USB

Universal Serial Bus. What made USB so wonderful is that you can connect up to 127 USB devices to your computer using a hub. Like FireWire, it is hot-plug compatible. This means you can connect and disconnect devices at any time and the computer can recognize it and you can also connect the device to any USB outlet. With the USB standard, there 6 common connectors.  However, the newest connector, type C, is meant to replace all other connectors. There is also currently 5 versions of the standard: USB 1.0, 1.1, 2.0, 3.0, and the just finalized 3.1. The primary difference in the version is the speed: the higher the version, the faster the data in the cable is. Because USB 3.0 (and 3.1) is significantly faster than 2.0, the cables will quite often have blue plastic inside the connector. USB 3.0 adapters may also be labeled SS for Super Speed. Each USB adapter is backwards compatible. You can plug a USB 3.0 device into a USB 1.0 connection and it will work. You can also connect a USB 1.0 device into a USB 3.0 connection and it will work. That is not the confusing part. The confusing part is the USB connectors.

Because USB cables send a little bit of power through them, manufacturers decided to make the phone charger and the computer connector one and the same. The power through the wire was originally meant to power devices such as a USB hub.

The USB type A connector is what you are probably most familiar with. It is a rectangle. With very few exceptions, this is the connector that goes into your computer or charger.

The USB type B connector usually connects to larger devices, such as printers. However, a USB type B version 3.0 or higher cable will not go into a USB type B 2.0 or earlier connector but a USB type B 2.0 cable can go into a USB 3.0 connector. As you can see in the picture above, a USB 3.0 type B connector has a little extra part on the top.

The USB type C connector is the newest standard. It is designed to replace all other USB connectors. Unlike all other USB cables, these are reversible and small. All you need is an adapter to convert any USB cable to a USB type C one. Computers are now just starting to implement USB type C adapters. So instead of a rectangle type A end on your computer and a square type B on your printer, you will have a type C adapter on both ends. And you also will not need to worry about which end is up because the cable is fully reversible.

The USB mini connector is found on small devices like cameras and remote controls, but that are not small enough for the USB micro connector.

The USB micro connector is found on very small devices, such as mobile phones and tablets. Like USB type B connectors, a micro USB 2.0 cable will connect to a micro USB 3.0 or later connector, but not the other way around. The above picture on the right is the USB 3.0 micro cable. Notice the extra piece on one side. You are probably familiar with the USB micro connector because almost every phone and device now uses it as a charger. However, very soon these devices will USB type C connectors for chargers.

The Apple Lightning cable is not a USB cable. It has a USB type A connector on one end and the Apple proprietary connector on the other. It was created by Apple for two reasons: (1) because USB cables are not reversible and having a reversible cable is just a good idea — which is why the USB type C connector was created. (2) because using Apple specific cables means that companies must pay an Apple tax to make equipment for their products.

VGA and DVI

There are two video standards for computer monitors. VGA is the oldest and it is the analog connector. DVI is newer and is digital. However, there is no video quality benefit from using a VGA cable or DVI cable. The only advantage of the DVI cable supports a higher resolution computer monitor than the VGA cable. That wasn’t too important until recently because the VGA cable supports HDTV resolutions.

The VGA connector is usually blue. But you can tell what it looks like because it has 3 rows of 5 pins. The maximum resolution of the VGA cable is 2048×1536 pixels for a 4:3 monitor, which is the aspect ratio of the old analog TV’s. HDTV’s are 1920×1080 pixels, so the VGA cable is more than adequate for a HDTV.

Digital Video Interface. The DVI connector is usually white.  The nice thing about this cable is that it includes all both the analog pins for the old VGA standard and digital pins. All this means is that all you need is an adapter to make your DVI computer’s connector a VGA connector. There are rare exceptions. If the connector on the your computer is labeled DVI-D, it is digital only. The maximum resolution for the DVI cable is 3840×2400 pixels for a 16:10 monitor, which is slightly higher than a 4K HDTV, which is 3840×2160 pixels. Before HDTV’s were mainstream, most widescreen computer monitors used the 16:10 aspect ratio. Very few monitors today are 16:10, most are 16:9 because of HDTV’s. (Very expensive high-end monitors still use the 16:10 aspect ratio.)

Of course, the primary advantage of digital is that it is all-or-nothing. The cheap cables deliver the exact same picture quality as the expensive ones. The only exception is if you buy some super cheap, usually Chinese made, knock off. If you buy a cable from a reputable distributor, the $5 cable works just as good as the $100 one.

HDMI

High Definition Multimedia Interface. This cable standard was designed to replace all audio and video cables for televisions. Many computer monitors support HDMI. The HDMI cable is backwards compatible with the DVI cable but the HDMI cable was not meant to be a replacement for the DVI cable. Although most computers support HDMI cables, this standard was not meant for computers. The standard size type A connector, displayed above, is almost always used. The only exception is that tablets or mobile phones may use a mini-HDMI, or type D, connector. HDMI type B and type C connectors are rarely used so they are not pictured above. The HDMI type E connector is meant for environments where it may wiggle loose, so it is a screw connector.

Here is where it gets confusing. There are several versions of the HDMI standard and they all use the same connectors and cables. The current standards are 1.0, 1.1, 1.2, 1.2a, 1.3, 1.3a, 1.3b, 1.3b1, 1.3c, 1.4, 1.4a, 1.4b, 2.0, 2.0a, and 2.1. HDMI 2.1 has yet to be released. Better audio and video quality requires more data to move through the cable, which requires better chips in audio/video devices. Engineers are always finding new ways to have better audio and video quality. The standards body also had to satisfy the ultra-paranoid movie studios who are afraid people might make digital copies of their movies. (P.S. the digital protection has already been cracked and like all anti-piracy measures, the only ones who are hurt are those who follow the rules.) This copy-protection is called HDCP — High Definition Copy Protection. If your new 4K HDTV did not support the 2.0a HDMI standard, your 4K HD movie would only play at HDTV quality. This is because the HDMI 2.0 standard did not support the latest HDCP standard but HDMI 2.0a did. This was a serious problem because when 4K HDTV’s first came out, most did not support HDMI 2.0a. The current maximum resolution of HDMI cables is 4096×2160 pixels, which is slightly higher than the 4K HDTV resolution of 3840×2160 pixels. 4096×2160 is the 21:9 aspect ratio found in almost all movies today. Some HDTV’s sold have the 21:9 extra wide screen aspect ratio.

DisplayPort

DisplayPort is a replacement for the DVI video cable. It is not meant to compete with HDMI. The purpose of HDMI is to make it easy to connect your equipment to your HDTV. The purpose of DisplayPort is connect your computer to your monitor. A good computer monitor is of a higher quality than a HDTV because you sit very close to your computer monitor unlike your HDTV. For that reason, DisplayPort is superior to HDMI in video quality. Unlike HDMI, you can daisy-chain multiple monitors through a DisplayPort cable. But the higher the resolution, the fewer monitors you can daisy chain. The maximum resolution of the DisplayPort 1.3 standard is 7680×4320 (8K) pixels. The DisplayPort 1.4 standard, which was finalized early 2016, allows 8K monitors to have the better color accuracy that 4K monitors already could have with the 1.3 standard. (Better color accuracy requires more data which is why lower resolution monitors already support the better colors but not the 8K monitors.)

The DisplayPort connector has two sizes: regular and mini. The only advantage of using the regular sized DisplayPort cable is that it does not wiggle loose easily. Like HDMI, DisplayPort allows audio over the cable.

DisplayPort also supports a technology called AdaptiveSync, also known as AMD FreeSync. Computer games can have some complex graphics. What can happen is visual artifacts can appear when playing these games because the computer video card is either drawing the image too fast or too slow. AdaptiveSync takes proactive steps to eliminate these artifacts.

Thunderbolt

This is a standard created by Intel, but it never really caught on. It was designed to be faster than USB and support more higher end hardware. For example, you can connect a video card through your Thunderbolt connector and to the computer it appear to be same as if it was inside your computer. It never caught on because (a) that and similar situations are hardly ever needed, (b) the faster speed of Thunderbolt was only needed for a few devices that are very expensive, (c) the licensing and design costs to use Thunderbolt are not worth it, especially since the USB cable has much less design overhead because of its familiarity.

But it is still around and still being developed by Intel. Thunderbolt version 1 and 2 use the mini DisplayPort connector. (Why? I don’t know.) Because of the design in Thunderbolt, the mini DisplayPort connector can also be used for a monitor or a Thunderbolt device. The Mac Mini is this way. It has two Thunderbolt 2 connectors. You can use any one of the Thunderbolt connectors for a monitor. The Thunderbolt 3 version uses the USB type C connector.

Because Thunderbolt offers little real world advantage over other long established standards, I don’t see it going anywhere.

Intel just recently made Thunderbolt an open, royalty-free standard. They wouldn’t have had to do this if Thunderbolt was catching on. And even after Intel did this, it still didn’t help adoption.

Ethernet/Network

There are several types of network wires, but we are only going to focus on the one for consumer products. The network wire (or Ethernet wire) is like a big phone cable, except with 8 pins. Only 6 pins are actually used however. The reason why it is 8 wires is because a phone wire can be 2, 4, or 6 pins and we don’t want network wires being confused with phone wires. There are 8 wires in the cable divided into 4 sets of 2 wires each. Each set of wires is tightly twisted. In a set, one wire sends the data as a positive voltage and the other as a negative voltage. However, two wires are reserved for sending electricity the devices. This is called Power over Ethernet (PoE). Twisting the wires and sending an equal but opposite signal reduces interference between wires. The tighter the wires are twisted, the less interference. Network wires are rated by categories. The higher the category the tighter the twisted pairs of wires and thus the faster the speed it supports. Generally speaking, most wires sold today are either category 5e, usually just called Cat5e, or Cat6. For home user, Cat5e cable is good enough.

The maximum length between the copper network wires is 330 feet before an amplifier or a network switch is required. However, most people do not run the cable more than 300 feet so that you have 15 feet of play on each end just to be safe.

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