Contains the full lesson along with a supporting toolkit, including teachers’ notes.
Over the past twenty five years, the mobile phone has evolved into a multi-function communications, media and internet device. Common functions today include the ability to store and play music, receive radio broadcasts, take digital photographs, check email and browse the web. Some phones incorporate satellite navigation systems.
In this lesson, we will look at some of the physical principles underlying the operation of today’s mobile phones. We will then see how the change from analogue signals to digital data facilitated convergence of technologies.
Early Development of Telecommunications
In 1800, Alessandro Volta invented the battery and it quickly became a sensation. However, the magnetic effect of anelectric current was not discovered until 1820. By 1840, a number of long-distance wired communications systems were in use. Distant electromagnets were switched on and off following a pattern of digital codes that represented letters of the alphabet. Wired transmission of analogue signals (voice or music) by wire was not achieved until the 1870s. In 1887, Heinrich Hertz demonstrated the propagation of signals over a distance without wires and within a few years these Hertzian waves (radio waves) were used for telecommunication. Initially, the transmissions were digital (using Morse code). In 1906, the first wireless transmission of analogue signals was achieved. Today the trend is from analogue technologies to digital.
Solid State Electronics
Prior to 1950, mobile mediaandcommunications technologies (radio and telephone) were largely confined to motor vehicle use. The invention of the transistor around 1950 and its application in electronics brought about a dramatic reduction in the physical size and power requirements of electronic equipment. In the 1960s, transistor radios were mass produced and were more affordable as they cost about a week’s wages. Portable tape recorders also arrived, enabling people to make their own recordings. A cassette tapecould hold about thirty audio tracks. These were analogue technologies. Cell phones, as we know them today, were not produced until the 1980s.