TELECOMMUNICATION

Communication over a long distance.

How the Telegraph Works

Sends electronic pulses over wire

Consists of: – Battery – Key (sender) – Wire – Sounder (receiver)

How the Telephone Works

Sound waves cause vibrations.

Transmitter – microphone that uses a diaphragm and carbon granules to produce a varying electrical current

Receiver – the microphone in reverse

Electronic telephones Cellular telephones (pages )

Transmission Channels

Copper Wire

Coaxial Cable

Optical Fibers

Microwaves – very short electromagnetic waves

Radio Waves – Amplitude: strength of the wave – Frequency: number of waves that pass a given point in one second

Radio

How Radio Works

Antenna picks up waves that have the station’s frequency.

How Television Works

Broadcast television signals are sent to an antenna.

The tv receives the signals and converts them to electrical signals.

The video and audio signals are separated.

Satellite Communication Systems

a device placed in orbit above the earth to receive messages from one location and transmit them to another

Geostationary orbit: 22,300 miles above earth traveling at the same speed as the earth rotates.

How the System Works

Signals are sent to orbiting satellites through earth stations.

Uplink: it receives signals and transmits them to the satellite.

Downlink: the satellite receives the signals and transmits them to another location back on earth