Lesson 5 - Analog Signals vs. Digital Signals Flashcards
Name a type of noise that develops from the voice transmission itself.
Echo
The signals found on many local loops would be a combination of __?__ and __?__ signals.
analog and digital
The signals for making a telephone connection are referenced as __?__ signals or __?__ signals.
control or supervisory
Name three signals that indicate a calling or called telephone.
dial tone
pulse
dial pulses (key tone)
Clear speech is contained best in a band or frequencies between __?__ and __?__ Hz.
200 Hz - 4k Hz
The range of frequencies for telephone circuits are said to be in the:
a. range of frequency
b. pass band
c. bandwidth
d. in-band
b. pass band
__?__ pass bands are limited to 300 Hz to 3,000 Hz. This signal is called a(n) __?__ signal.
Voice
In-band
Write the equation for expressing the signal power delivered to a load.
dB = 10 logio (P1 / P2)
What does 0 dBm stand for?
a. Decibel per 1 microwatt
b. Decibel per 1 megawatt
c. Decibel per 1 milliwatt
c. Decibel per 1 milliwatt
List three contributions to the degradation of a transmission system when information is being distorted.
bandwidth.
unequal amplification or attenuation of the various frequency components of the signal,
amplitude, noise, frequency
What is the effective standard set for idle channel noise in the U.S. network?
- 69 dBMO + to 180 180 mile
- 50 dBMO + to 3000 miles with -16 dBMO as speech level.
A plan called __?__ was devised so that a transmission path can carry many telephone conversations at the same time.
Multiplexing
Why are telephone system designs changing toward an all digital network?
Put into small space, low cost, operate with low power, have long-term reliability, has the option of adding more lines as a business grows, direct lines, extensions, key entry recognition for inbound calls, and internal paging, signal much simpler,
Discrete signal, represented as either changes in voltage or changes in light levels
Bits per second (for example, a T-1 line carries 1.544Mbps, and an E-1 line transports 2.048Mbps)
High bandwidth that can support high-speed data and emerging applications that involve video and multimedia
High network capacity; multiplexers enable multiple conversations to share a communications channel and hence to achieve greater transmission efficiencies
Good network manageability; smart devices produce alerts, alarms, traffic statistics, and performance measurements, and technicians at a network control center (NCC) or network operations center (NOC) can remotely monitor and manage the various network elements
Low power requirement because only two discrete signals—the one and the zero—need to be transmitted
Good security; encryption can be used
Low error rate; with twisted-pair, 10–7 (that, is 1 in 10 million bits per second) will have an error, with satellite, 10–9 (that is, 1 in 1 billion per second) will have an error, and with fiber, 10–11 (that is only 1 in 10 trillion bits per second) will have an error
__?__ electronics are becoming more cost effective than __?__.
Digital
analog
Are mixed signals an advantage or disadvantage with digital transmissions?
Advantage - same digital equipment can be used to process all digital signal sources.
The system that allows digital and analog interfacing is known as __?__.
BORSCHT
What do these acronyms stand for?
BORSCHT
SLIC
BORSCHT - allows digital and analog inerfacing (battery, overvoltage protection, ringing, supervision, coding, hybrid, and testing)
SLIC - subscriber interface, or subscriber line interface circuit - a group of basic circuits that power the phone and provide all basic functions of digital and analog interfacing furnished for each subscriber on a card - such as ringing, dial tone and dialing supervision.
Is increased bandwidth and advantage or disadvantage for digital transmissions?
Disadvantage
How can you avoid large timing differences?
Using a master clock source
What does bit stand for?
Binary digIT (each individual digital pulse - how much information is processed per clock cycle)
What do the following stand for?
PAM
PCM
PAM - Pulse Amplitude Modulation - - uses a carrier of pulses that originate at a constant frequency
PCM - Pulse Code Modulation - - binary signal transmitted in a serial form and the code varies as the signal changes.
Quantization causes:
a. background noise in the receiver.
b. busy signal
c. synchronized timing
d. sampling
a. background noise in the receiver.
Why is synchronous transmission more effective than asynchronous transmission?
It does not require the start and stop bits.
What telephone switching system is dedicated to one customer for their inner exchange?
PBX
How is a PBX connected to the central office?
2-wire circuit tip and ring, interconnects trunks with lines. Trunks connect the PBX to a central office, another PBX, or both.
For each phone connected to the PBX communication system is called a __?__ and usually has 3 or 4-digit extension.
Station - has a 3-4 digit extension.
