Operating instructions

CHAPTER 2 TECHNICALLY SPEAKING

Since PCs were developed before mouse technology, PC mice standards were developed ad hoc, free-for-all

and manufacturers developed three types of mice:

1) bus, which is archaic and now rare,

2) serial, and

3) PS/2, which IBM developed.

• The PC operating system must contain the appropriate driver to recognize the mouse signals. If the

computer does not contain the right driver, it cannot recognize the mouse. The use of dedicated

processors in NTI KVM switches ensures that each computer recognizes the mouse. Each processor

“emulates” the existence of the mouse even when the computer is not active on the switch. Thus, when

the computer is activated, it immediately recognizes the mouse movements and commands.

• As mentioned in the keyboard section above, Macintosh mice connect to a separate bus with the

keyboard. When you use a Macintosh mouse in a multiple platform configuration, the mouse emulates

the PC left- and right-button clicks. (See Table 2.)

• Sun computers use a totally different mouse with its own driver. Similar to the PC, Sun requires the

driver installation before the system can recognize the mouse signals.

Video Board Technology

Another differentiating feature in KVM switch construction is in the video board. Switching video without

degradation is a bit more difficult than switching the keyboard and mouse. This is an instance where the

quality of the components and careful engineering of the KVM switch makes a difference in the final output –

in this case, in video resolution and bandwidth.

In most KVM switches, the computer video signal travels through the Printed Circuit Board (PCB) on copper

traces. These conductive metal trails direct the individual signals to either the analog or digital switching

chips.

 Color signals (red, green and blue) go to the analog chip.

 Sync signals (horizontal vertical and composite synchronizing) go to the digital chip (TTL).

 The quality of the analog chip and PCB layout

determines its ability to handle high video and

bandwidths. Likewise, sync-switching chips

vary in their capacity to process digital signals.

 Switching chips allow only the signals from the

selected computer to proceed to the amplifiers

on the video board, which give the video

signals a little boost before they go to the

monitor.

As Figure 11 illustrates, video signals travel

through a number of conduits before they reach

the monitor. Like road surfaces influence the

lifespan of tires and the quality of the ride,

everything a video signal passes through wears

away at the video quality. Each connector and

integrated circuit is like a pothole; it has the

potential to destroy the quality of the video

signal. Because so much of the signal’s journey

igure 11 – Basic layout of a Video Switching PCB. The quality

of the components and engineering directly affects the quality of

the video output.