Chapter 1-2

Question 1

An analog circuit is composed of a pair of wires.
 One wire is the ground _________
 The other wire is the battery ___________
 These two wires power the analog phone

Answer 1

(positive) - tip

(negative) - ring

Question 2

Phone is lifted off hook
- phone connects the two wires
- electrical signal (\_\_\_ DC voltage) to
flow from the phone company
central office (CO) into the phone

Answer 2

Loop start signaling

48V

Question 3

The phone is picked up at the same
time as a call comes in but before the
phone has a chance to ring.

Answer 3

Glare

Question 4

a _________telephone has buttons for outside lines that are
pushed to directly access an outside line. Usually there is an
“intercom” button as well. Phones are answered by pushing
the button that the call comes in on, then lifting the handset.

Answer 4

key system

Question 5

Analog voice signals converted to Digital

 Requires _______ resources

Answer 5

Digital Signal Processing (DSP)

Question 6

Uses __________ to carry multiple conversations

 Eg. T1 carries up to ____ separate _____ channels

Answer 6

TDM (Time Division Multiplexing)

24

64Kbps

Question 7

Inband signaling (robs bits of information to carry
signaling)

Answer 7

CAS – Channel Associated Signaling

Question 8

 Out of band signaling (uses a channel to carry
signaling information)

 T1 lines use the __th time slot for signaling and E1lines
use the __th time slot.

Answer 8

CCS – Common Channel Signaling

24

17

Question 9

 Designed for larger, corporate environments
 Use ground start signaling
 Grounding of the wires tells the phone company to send a dial-tone
on the line
 Reduces Glare since a dial-tone is not received until the phone
company receives a ground signal

Answer 9

Private Branch eXchange:

Question 10

• supervisory signaling
• informational signaling
• address signaling

Answer 10

(on hook, off hook, ringing)

(dial tone, busy, ringback, and others)

(dual-tone multifrequency (DTMF) and Pulse)

Question 11

 _____ signaling sends the signaling in the same
communications channel as the voice.

 _____ signaling sends the signaling in a separate
communications channel from the voice.

Answer 11

In-band

Out-of-band

Question 12

Connects to the PSTN
and converts audio
into electrical signals.

Answer 12

Analog telephone:

Question 13

The link
between the customer
premises and the
telecommunications
service provider.

Answer 13

Local loop:

Question 14

Provides services to the devices on the local loop.

Answer 14

CO switch:

Question 15

Provides a connection between switches.

Answer 15

Trunk:

Question 16

Allows a business to operate a “miniature

PSTN” inside its company.

Answer 16

Private switch (PBX):

Question 17

: Typically connects to a PBX system.

Answer 17

Digital telephone:

Question 18

_______ is an international numbering plan for public
telephony systems:

 A valid number contains the following components:
 Country code
 National destination code
 Subscriber number

 Each number can be up to __ digits long.

Answer 18

E.164

15

Question 19

converting the analog wave into digital, numeric values

Answer 19

Quantization

Question 20

The average human ear is able to hear frequencies from

Answer 20

20–

20,000 Hz

Question 21

Human speech uses frequencies from

 Telephone channels transmit frequencies from

Answer 21

200–9,000 Hz.

300–3,400 Hz

Question 22

Sampling at twice the highest audio frequency used in the audio
can accurately reconstruct audio streams

 To reproduce frequencies from ____ Hz sampling would be
taken at twice ___, or ____

Sample “____ byte” of information ______ times per second.
 8000Hz * 8bits = 64,000bits of information per second.

Answer 22

Nyquist Theorem:

300–4,000

4000Hz

8000Hz

one

8000

Question 23

 Uncompressed
 μ-law used in North America and Japan
 When the high order bit is a zero
 a-law (used everywhere else).
 Used when the high order bit is a one

Answer 23

G.711

Question 24

 Applies Compression
 Reduces bandwidth to 8 kbps
 Two variants _______________
 a less processing, b adds VAD*

• VAD: Voice Activity Detection
• MOS: Mean Opinion Score

Answer 24

G.729

G.729a and G.729b

Question 25

The protocols of voice

Answer 25

 Real-time Transport Protocol (RTP)

 Real-time Transport Control Protocol (RTCP)

Question 26

RTP adds time stamps and sequence numbers
 RTP streams are one way
 two-way conversation requires dual RTP streams

Answer 26

 RTP Based on UDP

Question 27

RTCP’s primary purpose is statistics, for example:

Answer 27

 Packet count
 Packet delay
 Packet loss
 Jitter (delay variations

Question 28

RTCP uses the __________ port following the RTP port

Answer 28

odd-numbered