Technical information

© CLEAPSS 2005 1611 ICT in the Science Department
Projectors should have at least the following inputs.
• Computer (1 or 2 inputs)
• Video (TV picture signal)
• S-Video (higher-quality TV picture signal)
Many projectors also have a USB connection, allowing optional control facilities of the
computer from the projector’s hand-held remote control. Although most projectors
offer an audio input, the sound output from the internal speaker is rarely good enough
for classroom use and separate amplified loudspeakers are better.
Useful features on a projector
Optical zoom
To ensure that the image fills the screen, when the distance of the projector from
the screen is changed.
Keystone
adjustment
To ensure that the projected image has vertical edges, where the projector is sited
above or below the centre line of the screen.
Freeze
To retain the last picture shown on the screen, while the computer or other source
(such as a video microscope) is being set up or used for another purpose.
Hand-held
remote control
Offers facilities such as selecting input signals, blanking the screen and freezing
the picture (but keep spare batteries!). It also provides greater flexibility when
interacting with a presentation from any part of the room and is very useful for
operating a ceiling-mounted projector.
Installed projectors
Ideally, the projector should be a fixed installation in a lecture room or laboratory.
This avoids time-consuming setting up and reduces vibration risk, which may cause
lamp failure; lamps are extremely expensive to replace. A fixed installation should
also reduce the chance of theft during the daytime.
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The installation of a ceiling-mounted projector must be carried out professionally,
with proper supports, to a secure part of the ceiling.
Very occasionally, schools have reported problems with vibrations carried through the
ceiling from the room above the projector. This may result in picture shake or prem-
ature failure of the lamp. If this is likely, it may be preferable to mount the projector
on a wall at the back of the room. However, a special, more expensive, narrower-angle
projector lens may be required to project the same size image over a longer distance.
Cables from an installed projector should be routed to a wall or bench point. As a min-
imum, computer, video and S-video inputs to the projector should be available at this
point. This enables signal outputs from devices such as a computer, video player,
digital camera and digital microscope to be fed directly to the projector.
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lways avoid trailing leads across walkways or floors. Careful thought at the time o
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installation can avoid trip hazards from cables for years to come.
A mains switch for the projector should be accessible from floor level. However, it is
very important that buttons on the projector, or its remote control, are used to turn
the projector on and off, to ensure that correct shutdown and cooling procedures occur.
In a fixed installation, it is recommended that separate, power-amplified speakers are
fitted either side of the screen, The audio-input connections for these speakers should
be available at the wall or bench connection point described above.