Chapter 18 Science
Telephone messages are sent by
physical transmission
The smallest piece of electronically produced picture is called
pixel
Microwaves are used for sending telecommunication signals in
telephones
The area covered by each microwave relay antenna mounted on towers is called a
cell
One disadvantage of analog signals is that they
change continuously
Language is an example of a
code
To send sound using electricity, the first step is to
convert the sound into an electric current
Morse code was developed for
ship-to-ship and ship-to-shore communication
Over the telephone line, the sound waves from your voice are transmitted
signal by a transducer/microphone
A cordless phone is a
small transceiver
When you talk on the telephone, the sound waves of your voice are converted to an electrical signal by a
speaker cone
Each binary digit is called a
bits
A computer keyboard is an example of a
input device
Random-access memory, RAM, is contained on
microchips
A computer modem is
a modulator and demodulator
In 1989, the web was
a resource for scientific information
A code is
a set of rules used to interpret data that convey information
A digital signal is
a signal that can be represented as a sequence of discrete values
An analog signal
a signal whose properties such as amplitude and frequency, can change continuously in a given range
Optical fibers
a transparent thread of plastic or glass that transmits light
The transfer of information by means of electromagnetic waves through space is called
atmospheric transmission
All input devices provide data to the computer in the form of a
binary code
In a computer, the operating system is stored on
bios
Microwaves are a form of
electromagnetic radiation
For radio broadcast, sound signals are converted to
electromagnetic waves
The binary number system is associated with
electronic data
All the physical components of a computer are called
hardware
Television converts electromagnetic waves into
images and sound
A signal is a sign that represents
information
A computer monitor is an example of a
input and output device
A cathode-ray tub in black-and-white TV makes a beam of electrons from
negatively charged cathode
By the year 2009, all television signals will be broadcast
only digital high def called HDTV for short
When a computer is first turned on, the first program executed by the computer is the
operating system
During a telephone call, the incoming electrical signals are converted to sound waves by
transducer
The antenna of your radio receiver works as a
transducer
What is a satellite footprint
transmitting antenna of a communication satellite being aimed to cover the largest land area without becoming weak
Computers process binary data in groups of
zeros and ones
