The document discusses different types of audio-visual aids used in education, including non-projected aids, projected aids, overhead projectors (OHP), liquid crystal displays (LCD), bulletin boards, flannel boards, and interactive whiteboards. Non-projected aids include pictures and charts. Projected aids are images projected onto a screen using machines. OHPs project materials written on transparent sheets, while LCDs use backlights to display electronic images without emitting light themselves. Bulletin boards communicate information through posted materials. Flannel boards use cut-out pictures adhered to fabric-covered boards. Interactive whiteboards allow projection of computer displays that can be manipulated directly on the board.

1. PROJECTED AND NON PROJECTED AIDS
Audio visual aids may be divided into different types for the sake of
convenience. They are,
1. Visual or non-projected aids
2. Projected aids
These projected aids are of two types. They are,
I. Projected still pictures
II. Projected motion pictures
1. NON PROJECTED AIDS
It has been found by studies that about 75% of knowledge is received
through the eyes. This fact throws clear light on the significance of visual
aids in teaching-learning process.
2. PROJECTED AIDS
Projected Aids - Projected visual aids are pictures shown upon a screen
by the use of a certain type of machines. VALUES OF PROJECTED
AIDS Best motivators: - they are the best motivators the student work with
more interest. They are more attentive.

2. OHP
An overhead projector (OHP), like a film or slide projector, uses light to
project an enlarged image on a screen. In the overhead projector, the source of the
image is a page-sized sheet of transparent plastic film (also known as 'foils') with
the image to be projected either printed or hand-written/drawn. These are placed on
the glass surface of the projector, which has a light source below it and a projecting
mirror and lens assembly above it .They were widely used in education and
business before the advent of computer-based projection.
It includes,
 Optical system
 Condenser
 Focus adjustment
 Source of illumination
The overhead projector facilitates an easy low-cost interactive environment for
educators. Teaching materials can be pre-printed on plastic sheets, upon which the
educator can directly write using a non-permanent, washable color marking pen.
This saves time, since the transparency can be pre-printed and used repetitively,
rather than having materials written manually before each class. The overhead is
typically placed at a comfortable writing height for the educator and allows the
educator to face the class, facilitating better communication between the students
and teacher. The enlarging features of the projector allow the educator to write in a

3. comfortable small script in a natural writing position rather than writing in an
overly large script on a blackboard and having to constantly hold their arm out in
midair to write on the blackboard. When the transparency sheet is full of written or
drawn material, it can simply be replaced with a new, fresh sheet with more pre-
printed material, again saving class time vs a blackboard that would need to be
erased and teaching materials rewritten by the educator.

4. LCD
A liquid-crystal display (LCD) is a flat-panel display or other electronically
modulated optical device that uses the light-modulating properties of liquid
crystals. Liquid crystals do not emit light directly, instead using
a backlight or reflector to produce images in color or monochrome. LCDs are
available to display arbitrary images (as in a general-purpose computer display) or
fixed images with low information content, which can be displayed or hidden, such
as preset words, digits.
ILLUMINATION
LCD panels produce no light of their own, they require external light to produce a
visible image. In a transmissive type of LCD, this light is provided at the back of
the glass stack and is called the backlight. Two cold cathode fluorescent lamps are
mainly used for the illumination purpose.
SPECIFICATIONS
Resolution: The resolution of an LCD is expressed by the number of columns and
rows of pixels
Spatial performance: For a computer monitor or some other display that is being
viewed from a very close distance, resolution is often expressed in terms of pixels
per inch.
Temporal performance: the temporal resolution of an LCD is how well it can
display changing images, or the accuracy and the number of times per second the
display draws the data it is being given.

5. Color performance: There are multiple terms to describe different aspects of color
performance of a display. Color gamut is the range of colors that can be displayed,
and color depth, which is the fineness with which the color range is divided.
ADVANTAGES
 Very compact, thin and light, especially in comparison with bulky, heavy CRT
displays.
 Low power consumption.
 Little heat emitted during operation, due to low power consumption.
 No geometric distortion.
 The possible ability to have little or no flicker depending on backlight
technology.
 Can be made in almost any size or shape.
DISADVANTAGES
 Limited viewing angle in some older or cheaper monitors, causing color,
saturation, contrast and brightness to vary with user position, even within the
intended viewing angle.
 Subject to burn-in effect, although the cause differs from CRT and the effect
may not be permanent, a static image can cause burn-in in a matter of hours in
badly designed displays.

6.  In a constant-on situation, thermalization may occur in case of bad thermal
management, in which part of the screen has overheated and looks discolored
compared to the rest of the screen.
 Loss of brightness and much slower response times in low temperature
environments. In sub-zero environments, LCD screens may cease to function
without the use of supplemental heating.
 Loss of contrast in high temperature environments.

7. BULLETIN BOARD
A bulletin board is a board which is usually attached to a wall in order to
display notices giving information about something. In computing, a bulletin
board is a system that enables users to send and receive messages of general
interest. The bulletin board provided a forum for investors to exchange news.
Bulletin boards serve multiple purposes. They can convey a variety of information
from meeting announcements and parent news to curriculum overviews and
displays of student work. They can also make learning visible. Why: Bulletin
boards reflect a class or school's identity.
Bulletin boards can be used not only for classroom decoration, but as an
essential tool for classroom communication; between teachers and students as well
as teachers and parents, staff, visitors, or volunteers. There are four main types or
categories of bulletin boards that can (and should) be utilized in the classroom
including child-created, decorative, conceptual, and interactive.
TYPES OF BULLETIN BOARD
1. Child-created bulletin boards are an effective tool used in the display of
student’s work—art projects, writing prompts, science projects, etc. The
children feel a sense of pride, seeing their work displayed and knowing they
helped to create the bulletin board, while parents and visitors can enjoy seeing
the childrens' work and learning what has been going on in the classroom.

8. 2. Decorative bulletin boards are used to add color and aesthetics to the
classroom. In many cases, these are themed boards, following the seasons,
holidays, or other areas of interest. Many supply sites, such as MPM School
Supplies, offer themed bulletin board sets that can be recycled from year to year.
3. Conceptual bulletin boards compliment the subjects being taught in the
classroom or give more information on subjects that are found to be of interest
to the students. These boards are designed to illustrate concepts using pictures
wherein the visual representation helps students to understand the concept more
fully.
4. Interactive bulletin boards are designed to get the children involved. Made of
materials that are moveable/hands-on, these boards, when developmentally
appropriate, can help the formation of: students’ eye-hand coordination skills,
visual discrimination skills, left-to-right discrimination skills, one-to-one
correspondence skills, problem-solving skills, letter recognition, numerical
recognition, color recognition and small muscle coordination skills.

9. FLANNEL BOARD
A flannel board is a display board made of wood. Cardboard or straw board
covered with colored flannel or woolen cloth. Display material like the cut outs,
pictures, drawings and light objects backed with rough surface like sand paper
strips, etc, will stick to the flannel board temporarily. The sample paper backed
display materials can be detached easily and replaced with new relevant
material as the lesson progresses. flannel board or flannel gram is a storytelling
system that uses a board covered with flannel fabric, usually resting on an easel,
although its primary use is as a storytelling medium, rather than as a toy.
CHARACTERISTICS
 A flannel board of 1.5*1.5 m is most widely used. It can be fixed to next
to the chalk board or can be placed on a stand about one meter above the
ground.
 The display material can singularly adhered on the flannel board and then
removed for replacing it with the next material in a sequence for proper
development of a lesson.
USES
 For telling a story, the teacher adheres the picture on the flannel board
along with a commentary or description.

10.  For letter recognition and work formation during language teaching in
primary classes. This is done by cutting out big letters from chart and
backing them with sand paper strips.
 For recognition and recall testing, appropriate pictures can be used for
teaching different subjects.
 For teaching elementary lessons on numbers, a flannel board can be used
effectively.
 For showing inter relationship between different parts or steps of a
process, aflannel board can be used effectively.
ADVANTAGES
 The flannel board is simple and light to carry.
 Probably the greatest advantage of the flannel board is that it is a
dynamic medium.
 Changes can be shown by adding or taking away or transferring figures
or flashcards.
 They can be used over and over again for a wide variety of activities.
 A great way to get students attention.
 A tool to help keep children focused on what is being taught.
DISADVANTAGES
 Transportation and storing boards and materials is a problem.
 Spaceis usually limited.
 Time and costof making material is a problem.

11. INTERACIVE BOARD
An interactive whiteboard is a large, interactive screen that connects
a computer and a projector. The projector projects the computer's desktop
onto the screen of the interactive whiteboard. The user can control the
computer by using a special pen, finger or another tool to touch the screen of
the interactive whiteboard. Normally, interactive whiteboards are fixed
on walls. However, there are some mobile interactive whiteboards.
Interactive whiteboards are used in many different places such as
in classrooms, in work groups and in training rooms for professional
coaching. Interactive whiteboards are the modern version of the
traditional whiteboards used in schools. The first interactive whiteboards
were designed and manufactured for use in the office. They were developed
by PARC around 1990. This board was used in small group meetings and
round-tables.
USES
For Teachers:
 They can write onto the board and save it as a document for use in the other
lessons . You can also send the whole lesson or the documents via e-mail to pupils
who were absent.
 Interactive whiteboard makes it easy to demonstrate how to use new software
 Videos can be shown
For students:

12.  Fixing and changing ideas of a brainstorming easily is an resourcewhich students
can use to reach a success faster. When student can use modern technology they
are more interested in learning.
IMPORTANCE
 An interactive white board is a hardware device that is similar to a
whiteboard that is found in schools and also in businesses.
 It transmits any information written it to a computer or multiple computers.
 It is an instructional toolthat allows computer images to be displayed on to a
board using a digital projector.
 Extremely flexible tool which can be used with both the youngest primary
schoolchildren and university graduates.
 More costeffective than equipping an entire IT room or every student with a
laptop.
ADVANTAGES
 Improved learning.
 Increaed participation.
 Enhanced collaboration.
 Visual video presentation is possible.
 No time consuming.
 More attractive.

13. DISADVANTAGES
 Expensive
 Good technical knowledge
 Losing talented and dedicated teachers.