Chapter 2 Flashcards
converting analog data to digital signals is generally called
digitization
the electric or electromagnetic impulses used to encode and transmit
data
Signals
represented as continuous waveforms that can be at an infinite number of points between some given minimum and maximum.
Analog data and Analog signals
composed of a discrete or fixed number of values, rather than a continuous or infinite number of values.
Digital data and Digital signals
the height of the wave above (or below) a given reference point.
amplitude
the number of times a signal makes a complete cycle within a given time frame.
frequency
The length, or time interval, of one cycle is
called its
period
The range of frequencies that a signal spans from minimum to maximum is called the
spectrum
The ………. of a signal is the absolute value of the difference between the lowest and highest frequencies.
bandwidth
The ……… of a signal is the position of the waveform relative to a given moment of time, or relative to time zero.
phase
This loss of power, or loss of signal
strength, is called
attenuation
The ……… is a relative measure of signal
loss or gain and is used to measure the logarithmic loss or gain of a signal.
Decibel (dB)
the opposite of attenuation is called
Amplification
the process of sending data over a signal by varying either its amplitude, frequency, or phase is called
Modulation
The ……… digital encoding scheme transmits 1s as zero voltages and 0s as positive voltages.
nonreturn to zero-level (NRZ-L)
The ……… has a voltage change at the beginning of a 1 and no voltage change at the beginning of a 0.
nonreturn to zero inverted (NRZI).
the …….. encoding scheme has the following
properties: To transmit a 1, the signal changes from low to high in the middle of the interval, and to transmit a 0, the signal changes from high to low in the middle of the interval.
Manchester
The ……… digital encoding scheme was used in a now extinct form of local area network (token ring) but still exists in a number of unique applications.
differential Manchester
The Manchester encoding schemes are called
…….. because the occurrence of a regular transition is similar to seconds ticking on a clock.
self-clocking
The number of times a signal changes value per second is called the
baud rate
The ……… encoding scheme is unique among all the encoding schemes seen thus far because it uses three voltage levels.
bipolar-AMI
The ……. encoding scheme takes 4 bits of
data, converts the 4 bits into a unique 5-bit sequence, and encodes the 5 bits using NRZI.
4B/5B
The simplest modulation technique is
amplitude shift keying
Amplitude shift keying has what weakness?
It is susceptible to sudden noise impulses such as the static charges created by a lightning storm.
