This chapter
gets into the nuts and bolts of transmitting analog and digital signals over
various medium. It begins by explaining the four fundamental properties of an
analog signal. They are amplitude, frequency, wavelength, and phase.
- Amplitude – is a measure of its strength at any given point in time.
- Frequency – is the number of times that wave’s amplitude cycles from its starting point, it’s expressed in cycles per second or hertz (hz).
- Wavelength – is the distance between corresponding points on a wave’s cycle.
- Phase – refers to the progress overtime in relation to a fixed point.
Digital signals are comprised of
pulses which are positive voltages or zero voltages. This equates to a zero for
no voltage present or one if voltage is present. These ones and zeroes are characteristics
of the binary system. Every pulse in the digital signal is called a bit. Because
digital transmission involves sending and receiving only a pattern of 1s and 0s
it makes it more reliable then analogy transmission.
The text then goes into the sending
of these signals and data modulation and the direction of signals. If the
signal is traveling in one direction it is considered simplex. In half duplex
transmission, signals may travel in both directions over a medium but in only
one direction at time. Full-duplex can travel in both directions at one time.
It then leads into throughput which essentially is the measure of how much data
is transmitted in a given period of time, whereas bandwidth is the measure of difference
between the highest and lowest frequencies.
Some common transmissions flaws are
noise and attenuation. Both have negative impact on the signal strength. These
flaws can be caused by a number of issues such as type of connectors used, type
of wire used, and even installation methods. The chapter talks about the different
types of cables in great detail along with splicing techniques.
I found the chapter to have a lot of
good information. The material was understandable and presented systematically.
It was a good foundation chapter.
No comments:
Post a Comment