is energy traveling from one place to
another
A wave
- Discret, not continuous
- Can only have one or two voltage states
- Voltage jumps between 2 levels
- Made up of particular sine waves
Digital signals
- Continuous voltage
- Voltage varies as time progresses
- Typical of things in nature
- Many encodings possible
Analog signals
is a measurement unit important in
describing networking signals.
The decibel (dB)
measures the loss or gain of the power of a wave.
dB
Analyzing signals using an oscilloscope is
called
time-domain analysis
which is noise from
other signals being transmitted
nearby
Radio frequency interference
(RFI),
which is noise from
nearby sources such as
motors and lights
Electromagnetic interference
(EMI),
noise at the transmitter
or receiver of an optical signal
Laser
is an extremely important concept in
communications systems.
Bandwidth
, data signals are represented by
voltage levels that represent binary ones and zeros.
On copper cable
is used to transmit data signals by
increasing and decreasing the intensity of light to
represent binary ones and zeros.
Fiber optic cable
in order for the LAN to operate properly, the receiving
device must be able to accurately interpret the binary
ones and zeros transmitted as
signal levels.
is the decrease in signal amplitude over the length of a
link.
Attenuation
contribute to greater signal
attenuation.
Long cable lengths and high signal frequencies
Signal energy is also lost when it leaks through the ———– of the cable
and by impedance caused by defective connectors.
insulation
- If a connector is improperly installed on Cat5, it will have
a different impedance value than the cable.
Impedance Discontinuity
cause attenuation and jitter as a
portion of signal will be reflected back to the
transmitting device.
Impedance mismatch
the combination of the effects of signal attenuation and
impedance discontinuities is called
insertion loss.
(NEXT)
Near-end Crosstalk
(FEXT)
Far-end Crosstalk
(PSNEXT)
Power Sum Near-end
Crosstalk
are subject to the optical equivalent
of UTP impedance discontinuities.
Fiber links
