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How HDMI Cables Work

HDMI cables were first developed in 2003, and they have evolved over the past decade to provide a universal connection that combines both audio and visual channels into one interface. HDMI, which stands for high-definition multimedia interface, supports the connection between a device such as a Blu-ray player or cable box and a flat-screen HDTV or projector. The cables are also used for audio equipment such as mixers, recording systems and speakers.

The cable was developed by a partnership of some major electronics companies, including Hitachi, Matsushita (the parent company of Panasonic), Philips, Silicon Image, Sony, Thomson (the parent company of RCA) and Toshiba, which sought to establish a standard connection in the industry. HDMI cables use the same technology as DVI cables. DVI, or digital visual interface, is the digital connection standard in the PC environment. HDMI simply takes DVI and adds an audio component, support for a different color space and a few other components   all in a smaller connector. HDMI cables have become so well recognized that PCs and monitors sold today come with both an HDMI port and a DVI port from which to choose.

Prior to HDMI cables, each electronics company used various analog connections such as VGA, radio frequency and coaxial cable. HDMI combines video and audio interfaces into one connection, which simplifies the installation process of a home-entertainment system. The digital cable also substantially improves the quality of the picture and sound for everyone by providing the first standardized compact interface for transmitting this digital data in an uncompressed format.

Inside HDMI cables are conductors for both the audio and visual components. Both audio and visual components also have an audio return channel, which increases the speed and efficiency of their signals. Most conductors and the solder used to meld the conductors and connectors together are composed oxygen-free, high-purity copper, although some use silver as a solder. Silver and copper are the metals with the highest conductivity properties, but they also corrode when exposed to the atmosphere. The green tarnishing in copper and the dark gray tarnish in silver that can happen over time would affect the metals' conductivity. When the copper and silver that are used inside a cable are the highest grade possible, they have less chance of oxidizing or corroding over time.

On the outside, the standard cable connectors consist of 19 pins. The best HDMI cables coat the pins and external cap with 24-karat gold   a metal that resists corrosion very well and acts as a protector. Various materials are used for the external sheath that extends the length of the cable but these usually consist of various thicknesses of durable PVC plastic. Shorter cables can be more flexible, but longer cables, such as those used for in-wall installation, must be firmer to maintain the connection. HDMI cables were designed for long distances, and the best cables will support a connection up to 10 meters (32.8 feet) without the use of a repeater, a device that works to extend the signal.

HDMI cables have evolved over the past decade. The type A version of a high-speed HDMI 1.4 cable has a minimum bandwidth of 10.2 Gbps (gigabits per second) and supports a 1080p, high-definition screen resolution. However, the best cables support 3D and other advanced color spaces, which require a higher bandwidth and resolution. Mini HDMI cables, the type C version, support portable devices. They were designed under the HDMI 1.3 specification   an earlier version of the cables that support 720p. Mini cables have smaller connectors, but they still contain the 19-pin design of the larger cables.

Many of the cables available today also include Ethernet, which provides an internet connection in addition to the audio and visual components. The Ethernet connection does not affect the audio-visual components of the cable. As many devices that use HDMI cables today have the ability to connect to the internet, the Ethernet component simply eliminates the need for an additional cable or wireless connection. However, HDMI cables with Ethernet only work with devices that support the technology.

The best HDMI cables are future-proofed for technologies just on the horizon. The cables have standardized the uncompressed, audio-visual digital connection. They are used by many electronics devices today and have improved the picture and sound experience for everyone.