Let us have a look inside the HDMI cable!

HDMI cables are being used widely for connecting television and computer monitors. Most televisions have several HDMI ports these days. HDMI stands for High-Definition Multimedia Interface. It is the global standard for transmitting uncompressed digital video and multi-channel audio through a single cable.

Just like the coaxial cable with which we amateur radio operators are quite familiar, the HDMI cable also has an outer protective sheath. This one is probably made of polyvinyl chloride (PVC) for flexibility and durability. Beneath the jacket lies a braided metal mesh, often tinned copper, explaining the shiny lustre. The shield guards off radio frequency interference from external signals.

Inside the metallic mesh there is an aluminum foil layer. These together provide 100% coverage to block external radio frequency interference. Similar aluminium foil covering is there for modern coaxial cables used in amateur radio as well.

Here you can see several wires. Four of them are inside another coloured foil. The ‘free’ wires are in multiple colours, of which two are red coloured. They are all insulated wires and the violet one appears thinner than the others. There are a total of six ‘free’ wires.

The four foil coverings have two wires each inside them, making it a total of four pairs or eight wires inside the secondary foils.

One of the secondary foils have been opened to show the couple of wires inside. Now you know that the HDMI cable has a very complex structure inside, unlike the simple structure of our popular coaxial cables! Aluminium foil on each pair is meant to prevent crosstalk or interference between the wires.

TMDS (Transition Minimized Differential Signaling) is the “engine” of the cable, carrying all the actual video and audio data. These are the four shielded twisted pairs inside secondary aluminium foils. Three pairs will carry red, green and blue video channels, while one pair will carry the clock signal to keep the data synchronized.

Purposes of the other wires are for control, power and detection. Display data channels lets your TV tell your computer what resolution it supports. Consumer electronics control channel allows you to control multiple devices like a soundbar and TV with one remote. Internet sharing with other devices, providing a small power for communication chips even when the display is off and hot plug detection to tell the laptop when the display has been plugged in, are other functions.

Here is how the fully assembled HDMI cable looks like, though all of you will be too familiar with it.

End on view showing the multiple pin slots which will connect with the pins in the socket on the monitor or TV.

For completion sake, here is the other side, on the monitor.