Connectivity in Digital Signage Applications
Cables and connectors are often an afterthought in a digital signage installation. It is critical that customers select a high quality cable and the appropriate connectors for the hardware that they have selected. A customer always wants to make sure that the cable has been properly terminated to the cable so the signal is reliable. The other important aspect is the cable jacket. This is especially crucial when the area the cable is being installed into must meet certain electrical and fire codes like such as CMG, CL3, plenum or direct burial.Every digital signage system will need to have cables, even when the primary distribution method is wireless transmission. Connections from the wireless device to the source or display must still be made via a cable. The following connectors are the most common connector types used in the digital signage environment: VGA (also known as HD15), DVI, HDMI, DisplayPort, and RJ45.
VGA or Video Graphics Array refers to analog display standard for computers. Due to the widespread adoption of the technology, VGA has become the colloquial term used to describe the analog computer video signal that is produced or received by a computer or monitor as well as the HD15 connector. This signal and connector has long been the standard for computer video. The HD15 connector is a DB style connector that contains three rows of five pins for a total of fifteen pins. It is a very common connector on CRT monitors as well as most projectors and flat panel TVs.
Digital Visual Interface (DVI) is a video interface that was designed to replace VGA. There are two different types of DVI connector, DVI-I and DVI-D. DVI-I carries an uncompressed digital video signal and is also capable of carrying an analog video signal. DVI-I is most commonly found on computer video cards. DVI-D is a digital only signal that is normally the connector used on consumer gear.
The two different types of DVI connectors are distinguished by the pin configuration. Both connector types will have a grounding bar which is separate from the pins 3 rows of 8 pins. The DVI-I connector will have four additional pins that surround the grounding bar. The DVI-D connector does not have any pins surrounding the grounding bar.
High Definition Multimedia Interface (HDMI®) is a term that is used to describe a set of connectors as well as an uncompressed digital audio/video signal. HDMI® was the first uncompressed all digital interface that was able to carry both audio and video signals through a single cable. Though commonly found on consumer electronic devices such as a Blu-ray player, the HDMI® interface is now used as an audio/video output for laptops and desktops computers. It is also a very popular input on flat panel TVs and is getting more popular on projectors as well.
In addition to the audio/video signal and features, the HDMI signal includes content protection. High-Bandwidth Digital Content Protection (HDCP) was created by Intel to protect digital content such as movies and programming from unauthorized duplication. HDCP require that devices exchange information in the form of a digital handshake before content will be displayed. All of these signals, audio and video, features, and content protection, are carried by Transition Minimized Differential Signaling (TMDS).
DisplayPort is a digital display standard proposed by the Video Electronics Standards Association (VESA). The standard defines a royalty-free digital audio/video interconnect that is intended to connect a computer to a computer monitor or HDTV. This connector was designed to replace the VGA and DVI connectors that are commonly used for the video output of a computer. Though DisplayPort offers the same functionality as the HDMI connector, it is not expected to replace the HDMI connector in consumer electronics. The external connector has 20 pins and is secured by latch clips. This type of connector is found on computers, computer monitors, HDTVs, etc.
The RJ45 connector is the common modular connector used on twisted pair cable assemblies. "RJ" refers registered jack which is a standardized physical network interface. It uses 8 pins or conductors per connector. RJ45 connectors are often found on Category 5e or 6 cables to send an Ethernet signal between a modem and a computer's network interface card. The RJ45 connector can also be used to carry serial RS-232 control signals. In the digital signage realm, it can be found on commercial grade TVs, Ethernet switches, media players, as well as transmitters and receivers.
The transmitters and receivers are devices that are used to send an input video signal like VGA from a computer and send it over a RJ45 network cable from the transmitter to a corresponding receiver unit that will then display the VGA image on a TV. The benefit of using RJ45 cable with the transmitter / receiver unit is the distance you could run a network cable for much longer distances without being amplified. It is also easier to install and run a network cable.