Copper cables and Active Optical Cables (AOCs) connect video sources to displays over short or extended distances. But what if you need to extend more than just AV signals? For example, you need to remotely access and control a computer located in a secure data center far away from your workstation.
A keyboard, video, and mouse (KVM) extender is an ideal solution for this type of application. KVM extenders allow you to extend USB signals alongside video signals so you can remotely access and control computers from anywhere.
How Do KVM Extenders Work?
KVM extenders work in pairs: A computer connects to an extender unit that sends all output signals over a certain distance, commonly known as a transmitter. On the other side, a second extender unit receives the signals, commonly called a receiver. The receiver provides all the user interfaces needed to connect to the remote workstation: keyboard, video, and mouse.
There are many KVM extenders available today. State-of-art KVM extenders enable remote computer access and matrix switching with the high-fidelity experience of a desktop PC. They also support a large variety of additional peripherals such as audio, USB 2, USB 3, USB C, and serial control. These extenders even incorporate high-end features like video optimization, no matter the type of screen.
Next-generation KVM extenders are able to combine multiple types of signals and transfer them all over one wire. To do this, the transmitter performs the encoding and sends the signals over the line. The receiver acts as a decoder, restoring the data to its original source signals with next to no noticeable loss.
Copper Ethernet cable is the most common media used to transfer signals between transmitter and receiver units of a KVM extender. Ethernet cables are identified by their category, which indicates their transfer capabilities (for example, CAT5, CAT5e, CAT6, and CAT6A). KVM extenders that use copper cable are often called CATx extenders.
Although the extenders use Ethernet CATx cable to extend signals, they can transfer information using other proprietary protocols that are not compliant with the Ethernet and TCP/IP standards. This means that the extension range is limited to the cable length and cannot be increased with a networking device like an Ethernet switch. CATx KVM extenders commonly support cable lengths up to 100 meters (330 feet).
Fiber extenders work in the same way as CATx extenders, but they use multimode or singlemode fiber optic network cable as the transportation media. Most fiber extenders come with dedicated SC or LC multimode or singlemode connectors. Recently, fiber extenders with SFP ports that increase flexibility are becoming available. These extenders use SFP transceivers (Mini-GBICs) to adapt the link interface to the mode and length of the fiber cable that is often already installed in a building. Multimode extenders can extend signals up to 550 meters, while singlemode extenders can extend signals 10, 20, or even 40 kilometers. Like CATx extenders, fiber extenders also work with proprietary protocols and can only be linked directly with no Ethernet switches in between.
Recently, there has been a greater demand for KVM extenders that use TCP/IP packets to carry video and other signals. These extenders are known as IP-based or KVM-over-IP extenders, and they are the most flexible type of extenders on the market.IP-based KVM extenders connect to an Ethernet network and allow the system to leverage common network equipment to support extension and expansion.
IP-based extenders are becoming more popular because they are easy to deploy for IP-based point-to-point connections. However, system administrators need an extensive networking background and thorough knowledge of network capabilities to design, deploy, and expand an IP-based KVM system that can switch between multiple computers, users, and user access profiles.
About the Author
Aries Chuang has more than 25+ years of programming experience, as a product engineer, his primary focus are audio, video and networking, also provide firmware and software customize design for Black Box products.