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Video adapters explained
What is a video adapter?
Video interfaces and standards have evolved over the years so it's not uncommon for computers, video equipment and peripherals to "talk different languages" and support different features. You may want to use an older monitor as a second screen but your laptop doesn't support the video interface, or the only available laptop port is incompatible with your monitor. An inexpensive video adapter may be a lot cheaper than buying a new monitor.
Video signal conversion is similar to translating from one language to another. It is easy if both languages have a rich vocabulary but consider the case where one language has more words than another. For example, the latest edition of the Oxford English Dictionary contains more than 170,000 words but Chinese has only 83,000. Even for the most gifted translator, interpreting the precise meaning of an English conversation in Chinese would be challenging, and the reverse would require some creativity! Converting an audio video signal from a feature-rich protocol to a less functional format means discarding information and capabilities. For example, converting a DisplayPort 4K signal for display on a VGA monitor will typically yield a resolution of 1920 x 1080 (1080p) at 60 Hz. Note that most video adapters or adapter cables work in one direction only (e.g. from a DP port to a VGA monitor but not the reverse).
HDMI and DisplayPort are functionally similar video interfaces, but they use different methods of transmission (TMDS vs. LVDS). It is possible to connect a DisplayPort port on a laptop or PC to an HDMI monitor with no loss of image quality using a DP to HDMI adapter or adapter cable. If you use a passive cable, make sure the port on the video source is a DP++ (DisplayPort ++) dual mode port. If your graphics card does not support DP++, use an active cable such as Eaton's P582-006-HD-V2A.
DisplayPort to DVI
DisplayPort to VGA
Mini DisplayPort to VGA
High Definition Multimedia Interface (HDMI) is a standard for transmitting uncompressed audio and video between a source and a receiver or display. HDMI has been widely adopted and can be found on almost all televisions and computer monitors.
HDMI connectors are available in three sizes: standard, mini and micro. There are also different types of HDMI cable (Standard, High Speed, Premium High Speed and Ultra High Speed), each designed to support a specific video resolution.
HDMI to DisplayPort
HDMI to Mini DisplayPort
HDMI to DVI
HDMI to VGA (or VGA to HDMI) adapters
The 15-pin Video Graphics Array (VGA) connector first appeared on the IBM PS/2 personal computer in 1987 and was subsequently adopted by most PCs, as well as many monitors, projectors, game consoles and instrumentation. The connector is variously referred to as D-Sub 15-pin, HD15 or DB-15.
Even though the analog VGA interface has been largely replaced by digital interfaces like DVI, HDMI and DisplayPort, there is still a large number of older devices with VGA ports still in use. An adapter is required to convert to and from the VGA format.
HDMI to VGA (or VGA to HDMI)
Mini DVI adapters
DisplayPort to VGA
USB-C to VGA
Mini DisplayPort to VGA
DVI to VGA
You can connect a Thunderbolt 3 port to an HDMI display, but not directly. Thunderbolt 3 has native support for DisplayPort and from DP you can get to HDMI by way of an adapter. You can also use an adapter cable like Eaton's U444-006-H4K6BE to convert DP Alt Mode to HDMI.
USB Alt Mode allows a USB-C port to transmit non-USB signals, making it extremely versatile. For example, a laptop, Chromebook or Android phone with a USB-C port might use Alt Mode to output video to an HDMI TV or monitor without the need for an adapter. This is an important feature because the new, thinner laptops and tablets have a USB-C port but no HDMI port.
Odd as it may sound, you will need a USB-C port that supports USB Power Delivery to take advantage of USB HDMI Alt Mode, because it is the PD handshake that establishes an Alt Mode connection. You will also need a cable with a USB-C connector on one end and a USB-C or HDMI connector on the other. Older USB-A cables do not support Alt Mode. Another option is to use an adapter cable supporting DisplayPort Alt Mode, such as Eaton's U444-006-HDR4BE, to connect a USB-C port to an HDMI display.
An adapter or adapter cable can convert video from a USB-C or Thunderbolt 3 port to an older VGA monitor by using DisplayPort Alt Mode as an intermediate format. DisplayPort signaling is converted to VGA by a chip in the adapter. The resulting resolution of 1920 x 1200 at 60Hz is the maximum supported by the VGA interface.
When buying a USB-C to VGA adapter, keep in mind that not all USB-C ports support DisplayPort Alt Mode. Check your laptop or PC manufacturer's website or the owner's manual to make sure it supports USB-C Alt Mode prior to purchasing.
USB-C to DisplayPort
USB-C to Mini DisplayPort
USB-C to DVI
What's the Difference between TMDS and LVDS Signaling?
When digital data is transmitted, especially over long distances, it is susceptible to noise and signal loss. Differential Signaling is a way to protect it from interference as it travels from source to receiver. It works like this:
Low Voltage Differential Signaling (LVDS) is a widely used method of transmitting digital data. Its low-voltage, high-quality signal makes it ideal as an internal display interface for laptops, tablets and flat-panel displays. LVDS data is not encoded.
Transition Minimized Differential Signaling (TMDS) is a form of LVDS used in DVI and HDMI interfaces. TMDS signals are encoded so they have an equal number of ones and zeros, reducing the chance that the signal will degrade.
What is the difference between an active cable and a passive cable?
A passive cable simply passes the signal from one end to the other. The further the signal has to travel, the more it degrades, a process known as attenuation. That's why passive cables have a limited length. Active cables on the other hand include a signal booster that enables video and audio to be transmitted over longer distances. Active cables sometimes require a power supply to support signal conditioning.
How can I tell if a cable is passive or active?
Active cables have larger and slightly longer connectors to accommodate the circuitry necessary to convert and boost the signal.
What is DisplayPort Dual Mode (DP++)?
DisplayPort uses Low Voltage Differential Signaling (LVDS), which is not compatible with the Transition Minimized Differential Signaling (TMDS) used by DVI or HDMI. However, DisplayPort dual mode ports can transmit a single link DVI or HDMI TMDS signal using a simple passive adapter or adapter cable. Devices supporting dual mode will detect a DVI or HDMI adapter and send TMDS instead of LVDS signals. Note that dual mode is an optional feature and is not implemented by all device manufacturers, so check for DP++ support before purchasing. If your graphics card does not support DP++, use an active cable. Also keep in mind that DP++ is not bidirectional and does not support dual link DVI.
