A video port connects a monitor to a computer using a cable. Video ports and monitor cables transfer analog signals, digital signals, or both. Computers are digital devices that create digital signals. The digital signals are sent to the graphics card where they are transmitted through a cable to a digital display. Digital signals can also be converted to analog signals by the graphics card and transferred to an analog display. Converting a digital signal to an analog signal usually results in lower image quality. A display and a monitor cable that support digital signals should provide higher image quality than those supporting only analog signals. There are several video ports and connector types:
- Digital Visual Interface (DVI), as shown in Figure 1, has 24 pins for digital signals and 4 pins for analog signals. DVI-I is used for both analog and digital signals. DVI-D handles digital signals only, while DVI-A handles only analog signals.
- Displayport, as shown in Figure 2, has 20 pins and can be used for audio, video, or both audio and video transmission.
- RCA connectors, as shown in Figure 3, have a central plug with a ring around it and can be used to carry audio or video. It is common to find RCA connectors in groups of three, where a yellow connector carries video and a pair of red and white connectors carry left and right channel audio.
- DB-15, as shown in Figure 4, has 3 rows and 15 pins and is commonly used for analog video.
- BNC connectors, as shown in Figure 5, connect coaxial cable to devices using a quarter-turn connection scheme. BNC is used with digital or analog audio or video.
- RJ-45, as shown in Figure 6, has 8 pins and can be used with digital or analog audio or video.
- MiniHDMI, also called Type C, as shown in Figure 7, has 19 pins, is much smaller than an HDMI connector, and carries the same signals as an HDMI connector.
- Din-6, has 6 pins and is commonly used for analog audio, video, and power in security camera applications.
Display cables transfer video signals from the computer to display devices. There are several display cable types:
- High-Definition Multimedia Interface (HDMI) - Carries digital video and digital audio signals. Digital signals provide high-quality video and high resolutions (Figure 8).
- DVI - Carries analog, digital, or both analog and digital video signals (Figure 8).
- Video Graphics Array (VGA) - Carries analog video signals. Analog video is low quality and can be interfered with by electrical and radio signals (Figure 8).
- Component/RGB - Carries analog video signals over three shielded cables (red, green, blue) (Figure 8).
- Composite - Carries analog audio or video signals (Figure 9).
- S-Video - Carries analog video signals (Figure 9).
- Coaxial - Carries analog, digital, or both analog and digital video or audio signals (Figure 9).
- Ethernet - Carries analog, digital, or both analog and digital video or audio signals (Figure 9). Ethernet can also carry power.