Lesson 5 - Analog Signals vs. Digital Signals

Question 1

Name a type of noise that develops from the voice transmission itself.

Answer 1

Echo

Question 2

The signals found on many local loops would be a combination of __?__ and __?__ signals.

Answer 2

analog and digital

Question 3

The signals for making a telephone connection are referenced as __?__ signals or __?__ signals.

Answer 3

control or supervisory

Question 4

Name three signals that indicate a calling or called telephone.

Answer 4

dial tone
pulse
dial pulses (key tone)

Question 5

Clear speech is contained best in a band or frequencies between __?__ and __?__ Hz.

Answer 5

200 Hz - 4k Hz

Question 6

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

Answer 6

b. pass band

Question 7

__?__ pass bands are limited to 300 Hz to 3,000 Hz. This signal is called a(n) __?__ signal.

Answer 7

Voice

In-band

Question 8

Write the equation for expressing the signal power delivered to a load.

Answer 8

dB = 10 logio (P1 / P2)

Question 9

What does 0 dBm stand for?

a. Decibel per 1 microwatt
b. Decibel per 1 megawatt
c. Decibel per 1 milliwatt

Answer 9

c. Decibel per 1 milliwatt

Question 10

List three contributions to the degradation of a transmission system when information is being distorted.

Answer 10

bandwidth.
unequal amplification or attenuation of the various frequency components of the signal,
amplitude, noise, frequency

Question 11

What is the effective standard set for idle channel noise in the U.S. network?

Answer 11

• 69 dBMO + to 180 180 mile

- 50 dBMO + to 3000 miles with -16 dBMO as speech level.

Question 12

A plan called __?__ was devised so that a transmission path can carry many telephone conversations at the same time.

Answer 12

Multiplexing

Question 13

Why are telephone system designs changing toward an all digital network?

Answer 13

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

Question 14

__?__ electronics are becoming more cost effective than __?__.

Answer 14

Digital

analog

Question 15

Are mixed signals an advantage or disadvantage with digital transmissions?

Answer 15

Advantage - same digital equipment can be used to process all digital signal sources.

Question 16

The system that allows digital and analog interfacing is known as __?__.

Answer 16

BORSCHT

Question 17

What do these acronyms stand for?
BORSCHT
SLIC

Answer 17

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.

Question 18

Is increased bandwidth and advantage or disadvantage for digital transmissions?

Answer 18

Disadvantage

Question 19

How can you avoid large timing differences?

Answer 19

Using a master clock source

Question 20

What does bit stand for?

Answer 20

Binary digIT (each individual digital pulse - how much information is processed per clock cycle)

Question 21

What do the following stand for?
PAM
PCM

Answer 21

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.

Question 22

Quantization causes:

a. background noise in the receiver.
b. busy signal
c. synchronized timing
d. sampling

Answer 22

a. background noise in the receiver.

Question 23

Why is synchronous transmission more effective than asynchronous transmission?

Answer 23

It does not require the start and stop bits.

Question 24

What telephone switching system is dedicated to one customer for their inner exchange?

Answer 24

PBX

Question 25

How is a PBX connected to the central office?

Answer 25

2-wire circuit tip and ring, interconnects trunks with lines. Trunks connect the PBX to a central office, another PBX, or both.

Question 26

For each phone connected to the PBX communication system is called a __?__ and usually has 3 or 4-digit extension.

Answer 26

Station - has a 3-4 digit extension.