are only trustworthy up to about 35 feet (10.7 m) for
1080p signals. Their reliability for 4K is much shorter.
Although the VGA analog signal standard was sunsetted
several years ago and is officially obsolete, there
are still many schools and businesses using VGA computers,
laptops, and projectors. VGA cables typically
can reach out to about 100 feet (30 m).
For standard USB 2.0 cables, the range is approximately
16 feet (4.8 m), but it is reduced to only 10 feet
(3.0 m) when used with USB 3.x devices.
Signal extenders are available to extend all these
signals over Category cable using a variety of technologies.
To accommodate today’s high-bandwidth ultra-
high-definition HDMI signals in an educational environment,
deploying extenders may be a good option because
they reduce system complexity while fitting within
a school’s limited budget; simple control capabilities
are an easy add-on.
Using a system built on HDBaseT technology
embraces that simplicity by allowing the integration
of multiple signals on a single system and cable, covering
the full range of AV technology. HDBaseT is an industry
standard that provides high-definition HDMI extension
Below are recommended maximum lengths for different AV links,
compared to maximum lengths using AV extenders:
HDMI Cable
USB 2.0 with Extender
over Category cable
USB 1.1 with Extender
over Category cable
October/November/December 2019 I 19
Teachers in classrooms from kindergarten to college
require AV systems that allow them to extend HDMI and
USB signals from their desks to output devices located
throughout the classroom. To accomplish this, some
school administrators lean toward installing complex,
professional AV systems with multiple touchscreen inputs
and controls. Although these systems can meet the technological
needs of classroom AV equipment, using them
effectively is often beyond the skill set of teachers and AV
club members alike, thereby requiring professional
installation, system set-up and maintenance by IT
managers, and extensive training to operate.
Classroom AV systems should not be complex. In an
educational environment, a simpler system encourages
student engagement, integrates easily into the learning
setting, and upgrades for a longer life solution. A simple
system is far more likely to accommodate the classroom
infrastructure, school budgets, and end-user needs.
When designing an AV system for a classroom setting,
there are three keys to a positive user experience:
1. Extension for AV signals
2. Minimal components
3. Intuitive interface and easy controls
1. EXTENDING SIGNALS:
KNOW WHEN PASSIVE
AV CABLES ARE
NOT ENOUGH
HDMI®
100 m
328 ft
12-15 m
40-50 ft
VGA
(Obsolete)
100 m
328 ft
30 m
100 ft
USB
100 m
328 ft
50 m
164 ft
4.8 m
16 ft
HDBaseT 100 m Extender
over Category cable
VGA with Extender
over Category cable
VGA Cable
USB 2.0 Cable
Just as building infrastructure varies in
age from school to school so too does the
network infrastructure. Cat 5e, Cat 6,
and Cat 6A UTP cabling can all be found
in educational institutions today. In many
school districts, passive cables have been
the standard for AV systems for years, but
passive cables will not provide adequate
support for 21st century classroom
AV signals.
Most AV applications will require some
form of signal extension (Figure 1). For
example, HDMI cables are specified to be
operational at lengths of 40 to 50 feet
(approx. 12 to 15 meters). However, they
FIGURE 1: Recommended maximum lengths for different AV links,
compared to maximum lengths when using AV extenders.