Operating instructions

CHAPTER 2 TECHNICALLY SPEAKING
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TECHNICALLY SPEAKING
KVM Switch construction differs from manufacturer to manufacturer, as does the engineering of switch
products. There are differences in the processor configuration, video board engineering, and keyboard and
mouse recognition and connectors. Different manufacturers have different On Screen Display (OSD) software
configurations. Each manufacturer has their own way to present control/switching methods. This section will
explore in more detail different aspects of KVM switch technology.
EVOLUTION OF KVM SWITCHING
There are two types of KVM switches, mechanical and electronic:
MECHANICAL KVM SWITCHES
Mechanical switches (or passive switches) use no electronics or intelligent circuitry. Mechanical KVM switches
require that the user physically turn a rotary switch to open the computer port channel through which
information is passed.
Benefits
 While mechanical switch procedures can become tedious for large configurations, mechanical switches
could fit the bill in small installations, such as Small Office/Home Office (SOHO) environments. In these
situations, mechanical KVM switches help keep costs down.
Limitations
 Limited to manual switching. Users must physically turn a rotary switch to open the computer port channel
through which they want to pass information. These passive devices cannot communicate with the
computers at the end of each closed channel or interpret the information that passes through the switch.
 Each computer must be booted up individually. While the rotary switch is at a particular computer port, the
user can turn that computer on (or “power up”), but then must wait for it to completely boot up (turn on and
perform “self-tests”) before going to the next computer.
 Mechanical KVM switches often lose the keyboard and mouse on closed computer port channels, which
results in errors that require you to restart the affected computer.
 Low video resolution (800x600 maximum) – users who have monitors which have a higher resolution and
who use a mechanical KVM switch will not receive the full advantage of high-resolution display.
 No PS/2 mouse support (serial mouse only) – users who do not have a serial mouse for the mechanical
KVM switch will need to purchase one.
E
LECTRONIC KVM SWITCHES
Electronic KVM switches (or active switches) operate on the same principal as mechanical switches, but utilize
one or more microprocessors to communicate with the computer. The processor(s) in the KVM switch works
like any CPU. The function of the processor is to tell the switch how to “process” data received from keyboard
or mouse signals and what to display on the monitor. There are two types of electronic KVM switches – those
with one shared microprocessor and those with individual microprocessors.