in July 2005
By Bret Emerson, RCDD/NTS
Connectors and cabling play a key role.
Everyone is aware of the mantra
in the real-estate industry: Location, Location, Location.
The last few years have brought a similar refrain to the audio/video
and information technology industries: Convergence, Convergence,
Almost every article you read has
some reference to how one system or another was “converged”
with another system to provide the customer an advantage in
cost or ease of installation and management. The convergence
that we read about usually deals with Internet Protocol (IP),
which means routing your information via an Ethernet network
that may or may not be able to be extended across the internet.
Another distinct aspect of this convergence
is more physical in nature. It has to do with the connectors
and cabling that are being used in structured cabling systems
for new and renovated communications infrastructures. As technology
has invaded our educational system, for example, communications
engineers and cabling vendors have begun to adapt how they
think about cabling and wiring the rooms to meet these new
audio and video requirements.
Most K-12 schools that are undergoing
a renovation or building a new school have some money earmarked
for technology. In the past, this meant Cat5e cabling to the
rooms for data and telephones, and maybe a coax cable for
a TV mounted in the corner. As the audio and video systems
have become more of an integral part of the learning process,
there has been a shift in the infrastructure cabling and connector
This full-view of the television,
desk and lower converged faceplate shows how the TV could
be connected to an alternate audio/video source that might
be at a desk or rolled in on a cart.
More Use of UTP Cabling
More and more of the audio and video
signals are utilizing Unshielded Twisted Pair (UTP) cabling,
whether it be Cat5e, Cat6 or even the pre-standard Cat6A.
This convergence has meant that classrooms require connectors
in the rooms that serve data networks, telephone system and
audio/video systems. This is of particular consequence when
the classroom includes advanced AV such as ceiling-mounted
projectors and sound-assist systems.
Almost every school district wants
to implement digital video projectors in the classroom. Projectors
and PCs have become such a large part of the teachers’
lesson plans that there are numerous stories where a teacher
will conveniently “forget” to return the projector
cart that he had signed out for the day, just to be able to
use it for a class the next morning. Alongside the projector,
many districts want to install sound-assist systems in the
Sound-assist systems typically consist
of a wireless microphone, a mixer/wireless receiver/amplifier
and speakers in the ceiling or on the wall. These are used
to enhance the voice of the teacher, with the theory being
that students learn better and pay closer attention when they
hear the teacher’s voice coming from “everywhere”
in the room. Some of the sound-assist systems allow alternate
audio inputs to amplify not only the microphone signal but
signals from up to three other sources.
This integration of audio and video
signals with the IT infrastructure has required that many
of the communications engineers who used to deal just with
unshielded twisted pair (UTP) cables must now design infrastructures
that include the audio and video systems and cables.
In the design of these systems, we
must realize that most K-12 classrooms still use a mostly
lecture-style teaching arrangement. Integrating projectors
and technology means ceiling mounting the projector and ceiling
speakers and then routing all the cable to a faceplate at
the teacher station or desk. The teacher station at most schools
serves as the technology cabinet and usually has a PC, VCR/DVD
player, sound-assist amplifier, and maybe a printer and possibly
an Ethernet-based control unit.
Any of these Cat6 cables that
route back to the panels in the communications room could
be used for transmitting video and audio signals between
classrooms or back to the video distribution headend equipment.
Integrating the Signals
The physical aspect of this AV/IT
convergence is to try to integrate all the input signals and
output signals to work as one communications infrastructure.
One of the more important things to look at when designing
the cabling infrastructure inside a school, as well as inside
the classroom, is how to deal with all the telephone and data
signals and the new audio/video signals while providing a
single faceplate that hopefully has connectors for all these
systems. Some manufacturers are farther along in their audio/video
product lines than others. It runs the gamut from manufacturers
just providing F-connector pass-thrus to manufacturers offering
HD-15 VGA connectors with screw connectors on the back.
There are numerous options when integrating
audio/video into classrooms, from the simple solution of installing
a television in the corner of the room to installing a video/audio
switcher in the teacher station and tying that into a control
unit and ceiling-mounted video projector. The decision process
usually is based on the amount of money available and the
complexity of the system the teachers will tolerate and be
able to use.
Most of the schools today settle
on a system that includes a video projector that acts as the
video switcher and a sound-assist system that acts as the
mixer for the audio from the PC and VCR/DVD player. They also
want a control system that allows the teacher to use his PC
to turn on the components and switch the projector between
the different video inputs. The control system also connects
to the IP network to allow a centrally located IT professional
to view and remotely control the AV systems in each classroom.
One of the biggest issues teachers
have with technology in the classroom is that sometimes it
doesn’t work and many times they have to wait up to
a week for a tech assistant to visit their room to fix the
problem. The IP control system allows the IT professional
to connect remotely to the classroom control system and diagnose
and fix something that may be as simple as changing the video
input on the projector.
Pushing for Simple Solutions
As these systems invade the classroom,
cable and connector manufacturers are being pushed to provide
simple solutions that integrate all the connectors into one
faceplate. Some of these manufacturers have taken the next
convergence step and are providing audio and video modular
connectors that fit into their standard faceplates and use
Cat5e or Cat6 cables for transmission of the AV signals.
The racks in the main communications
room provide a central location for Cat6 cables and fiberoptic
cables installed throughout the building.
On the wall near the teacher station,
the incoming Ethernet and telephone connections are terminated
on Cat6, eight-pin modular connectors. The CATV cable is terminated
with an F-connector and then attached to an F-connector pass-thru.
For years, many of the manufactures have been providing the
Cat6 jacks and the F-connector pass-thrus that fit into their
faceplates. Beyond these standard connectors, it depends on
the manufacturer’s dedication to the integration of
AV signals with IT infrastructure as to whether it provides
a full complement of AV connectors that also fit into its
faceplates. Check with your local dealer representative to
see if your favorite manufacturer provides a complete line
of AV connectors.
Manufacturers that our communications
engineers recommend are providing multiple audio and video
connectors. The connectors come in many different styles:
pass-thrus for pre-terminated cables, solder connectors that
attach directly to the connecting cable on the back and to
the patch cable in the front, screw-type connectors on the
back with female or male connectors on the front. And the
most IT-integrated connectors have an audio or video connector
on the front and a 110-style connector for UTP cables on the
back for connecting to a Cat5e or Cat6 cable.
Everyone in the audio/video industry
is aware of the different baluns and connectors that allow
users to send video and audio signals via Cat5e or Cat6 cable
over long distances. High-end designers probably would use
custom-designed faceplates and industry-standard connectors
and cables for transmitting signals between the sending and
receiving units in their audio and video systems. In schools,
where the audio and video signals are simply within the room,
and at most have to extend 20 feet from faceplate to the projector
or speaker, these connectors that fit into the IT faceplate
provide a simple interface that allows one faceplate to be
used for IT and AV signals.
The biggest issue in integrating
AV into the IT faceplate has been with the RGB/HV signal and
trying to transition from an HD15-VGA connector on the front
to a five-strand mini-coax cable on the back. Some vendors
make a VGA to BNC transition cable that is as short as six
feet long. This still doesn’t work because there is
no space in even a double-gang box to hold the transition
cable as well as the other Cat5e and coax cables. This has
led to the introduction of an HD15 female to screw-down connector
that allows the contractor to use a five-strand mini-coax
cable for connection from the faceplate to the projector.
The snap-in VGA connector provides
a standard HD-15 pin connector on the front, while providing
an easy-to-terminate screw-down connector on the back
for connection to a five-strand mini coax cable.
At the faceplate, the HD15 on the
front transitions through a circuit board to a screw-down
connector that has connection points for each coax and their
shields. The coax cable then extends through the ceiling and
is terminated with five BNC connectors at the projector. For
the short distances that the video signal has to travel, this
solution works wonderfully, while allowing space for other
cables and connectors to utilize the same faceplate.
This solution takes care of the PC
signal, but that still leaves the composite signal from the
VCR and the S-video signal from the DVD player, not to mention
the speaker connections from the sound-assist amplifier.
Where the S-video and composite video
signals used to be connected via pass-thru connectors, one
simple solution is to use a connector with the video connector
on the front and a two-pair UTP connector on the back. This
allows you to use one Cat6 cable to transmit both the S-video
and composite video signals. Route the Cat6 cable from the
back of the faceplate and up to a faceplate in the ceiling
near the projector that has the same connectors; from that
point, simply run an S-video patch cable and an RCA-style
composite video cable from the faceplate to the connectors
on the projector.
The speaker level signal that comes
out of the sound-assist system can be routed through screw-type
speaker posts that mount directly into the faceplate. This
allows the speaker cables to be terminated on the back of
the jack and then use banana-style connectors on the front
of the faceplate.
The education market is different
from high-end presentation venues, and even university lecture
halls. Each school has a fixed amount of money to use when
upgrading its communications systems. The job of the communications
engineer is to help the school choose the best products that
allow its teachers to use technology in the classroom, while
working with the architect to integrate the cabling and systems
into the look of the building.
This view of a double-gang, converged faceplate details
the connectors on the front that the user sees, and
the actual cable interface on the back. This could be
used to connect a teacher station equipped with a PC
and VCR/DVD player to a projector and speakers in the
Labeling is important for
tracking cable routing. Whichever product you choose
should allow for labeling of all the connectors in the
Converged faceplates and connectors
allow owners to use the same faceplate for data and
Some May Cringe
Some AV designers may cringe at the
use of Cat6 cables for video, utilizing screw-down connectors
for RGB/HV signals and banana connectors for the speakers,
but this trend toward physical integration at the faceplate
is only going to expand as the march of IT and AV convergence
continues. Cabling manufacturers are going to continue to
innovate and provide audio and video connectors in their plates
to try to capture some of the AV market that they used to
lose to the specialized faceplate and connector manufacturers.
As communications engineers working
in the education market, we strive to balance the requirements
of both the owners and the systems themselves: Choosing products
that will provide the quality required to successfully transmit
the AV and IT signals, while also keeping an eye on the financial
costs of the installation and the “look” that
the architect and interior designer want to convey. This comes
down to a balancing act that is being assisted by manufacturers
that see the value in the AV and IT convergence, and are making
products to make these installations easy and cost-effective.
Bret Emerson, RCDD/NTS, president
of CommTech Design, a communications engineering firm in Grand
Rapids MI, makes presentations and has written numerous articles
regarding the need to include communications engineers in
the building-design process. Where technology used to be an
afterthought, it now should be discussed and designed just
as the electrical and mechanical systems are designed.