P1bL4 Telecommunications

Key Words

Communications satellite - satellite orbiting the Earth receiving and relaying microwave radio signals.

Digital signals - electrical signals consisting of a series of ON and OFF pulses.

Fibre optics - fine strands of glass which transmit digital pulses as flashes of light.

Geostationary satellite - a satellite that orbits the Earth every 24 hours, thus staying in one place above the ground

Telecommunications - using EM radiation to transmit data over long distances.

Grade E

Electromagnetic waves are central to modern telecommunications which have brought so much benefit to our society.

• Radio waves are used for local broadcasting;
• Microwaves transmit digital signals to satellites. 
• Infra red lasers transmit digital signals down fibre optic cables.  Our telephone conversations are transmitted like this.
• High speed internet connections rely on digital technology.

Digital radio and TV broadcasts are very common.  Mobile telephones use digital technology.

Grade C

Modern telecommunications use digital signals.  A digital signal looks like this:

It's a series of electrical pulses of ON (1) and OFF (0).  However, we hear, speak, and see in analogue signals that look like this:

So the signals have to be converted into digital form for transmission, and turned back into analogue form for us to understand.    Computers use digital signals, but have lots of circuits to turn the digital signals back into something we understand.

Signals are sent in a narrow beam to a communication satellite high above the Earth and relayed back to another ground station:

Many cities rely on systems like this, rather than underground cable.  This avoids having to dig up roads to lay cables which is expensive and causes a lot of annoyance to residents.

Grade A

Geostationary satellites remain above the same point on the ground.  They orbit the Earth every 24 hours, at a distance of 36 000 km.