1. The Telephone transmitter loudspeaker (Sound energy to
electrical energy)
(Electrical energy
to sound energy)

2. Printed circuit board of the telephone

3. An Older Telephone

4. Using an oscilloscope 1) Quiet sound, low frequency:
2) Quiet sound, high frequency:
3) Loud sound, low frequency:
4) Loud sound, high frequency:

5. Telecommunication Optical Fibres
The law of reflection.
When a ray of light bounces off a mirror , the angle going in equals the angle coming out.
The line at right angles to the mirror is called the normal.

6. Optical Fibres
When light is incident on a glass surface, refraction or bending of the light takes place.
The light comes out of the glass.
This however is dependent on the angle i.

7. Finding the Critical Angle…
1) Ray gets refracted
2) Ray still gets refracted
4) Ray gets internally reflected
3) Ray still gets refracted (just!)
THE CRITICAL ANGLE

8. Optical Fibres Optical fibres are made of thin flexible glass threads.
They are about the size of a human hair.
The fibres have a protective coating which keeps the light inside the fibre.

9. Satellites Interactive summary.
Satellites which orbit the earth every 24____ are called ________ satellites.
They are above the _____ point on the _____ .
Satellites use ______ dishes to _______ the microwave signals.
The microwave signals travel in _______ lines.