BNT 2025 Reviewer

POTS refers specifically to the traditional analog telephone service that operates over copper wires, facilitating basic voice communication.

Plain Old Telephone Service (POTS)

PSTN is the broader global network of interconnected telephone systems, which includes both analog (POTS) and digital technologies like fiber optics and Integrated Services Digital Network (ISDN).

Public Switched Telephone Network (PSTN)

_______: Voice

_______: Voice and Data

Plain Old Telephone Service (POTS): Voice

Public Switched Telephone Network (PSTN): Voice and Data

is a system of communications employing an apparatus that transforms a sound wave into an electrical wave, transmits the electrical wave over a suitable medium, and then transforms the electrical wave back into a sound wave at the receiver

-focuses on voice communications

-traditionally wire communications

-may be wire or wireless

Telephony

telephony block diagram

subscriber (old telephone) ---subscriber loop---central office

telephony according to sir matias is all about ________

switching

what is a central office?

switching ng calls

used standard voltage for telephone exchanges (central offices) to avoid corrosion (using a negative voltage reduces electrochemical corrosion in copper wires, prolonging their lifespan.)

-48V DC

key stages in a traditional telephone call setup

1. offhook

2. dial tone

3. addressing (tone dialing)

4. line status evaluation

5. call established

6. onhook

Voice Channel

Europe:

North America:

Nominal Voice Channel BW:

Voice Channel

Europe: 300Hz-3400Hz

North America: 200Hz-3300Hz

Nominal Voice Channel BW: 4 kHz

key stages in a traditional telephone call setup

1. _______

-When you lift the handset, the telephone switch detects a change in loop current (caused by completing the circuit in a -48V DC loop).

-This signals to the exchange that you want to initiate a call.

-nakaangat yung plunger ng telephone

OFFHOOK

key stages in a traditional telephone call setup

2.___________

-The central office (CO) or PBX sends a continuous tone (350Hz + 440Hz in North America) to indicate the system is ready to accept input.

-If no input is received within a timeout period, the call attempt is canceled.

DIAL TONE

key stages in a traditional telephone call setup

3.____________

-You dial the number using either:

DTMF (Dual-Tone Multi-Frequency) - modern phones send tones for each digit.

Pulse Dialing - older rotary phones break the loop circuit in a specific pattern.

-The exchange interprets the digits and determines the route to the destination.

ADDRESSING (TONE DIALING)

key stages in a traditional telephone call setup

4. _____________

The exchange checks whether the called number is busy or idle

A. if busy

_________

B. if idle

________

LINE STATUS EVALUATION

A. if busy

(440Hz + 480 Hz)

B. if idle

(480Hz + 620 Hz)

key stages in a traditional telephone call setup

5.___________

-When the recipient answers (also goes Off-Hook), the exchange connects both lines.

-Two-way voice communication is established.

-The exchange maintains supervision, monitoring the line for disconnect events.

CALL ESTABLISHED

key stages in a traditional telephone call setup

6. _________

-When either party hangs up, their phone breaks the DC loop (no more current flow).

-The exchange detects this and disconnects the call.

-If only one party hangs up, the other hears a reorder tone (fast busy) until they also go On-Hook.

-nakababa yung plunger ng telephone

ONHOOK

SIGNAL IMPAIRMENTS (AND)

ATTENUATION

NOISE

DISTORTION

ONHOOK means

OFF HOOK means

ONHOOK means NO DC CURRENT FLOW

OFF HOOK means DC CURRENT FLOWS

WHEN DIALING

DC:

AC:

WHEN DIALING

DC: (dial tone) ->busy signal

AC: ringing signal and ringback signal

Tone dialing ->

Tone dialing -> Dual tone multi-frequency

minimum sampling rate must be satisfied to avoid _________

aliasing

fs(min)=2fa

if there is no fa or BW given consider ____. standard fs(min) is ______

4KHz

8KHz

telephone service as as an __________

waveguide act as _______

low pass frequency

high pass frequency

parallel to onhook/offhook circuit, equalizer circuit and hybrid yung ___________

ringer circuit

components of basic telephone set

- hook switch (cradle switch)

- dial assembly

- ringer assembly

- handset (containing Tx and Rx)

ringer assembly

green

red

yellow

white or black

green -> tip -> transmit

red -> ring -> receive

yellow -> slave phones (extensions) party line configurations or setups where multiple phones shared a single ring generator

white or black -> ground

subscriber loop design\resistance design:

RDC=0.1095/d^2

RDC -> ohms/miles

d -> inches/mils (finals ans)

subscriber loop requirements

-enough current/power to "activate" switches, telephone, transmitter/receiver, etc.

-minimum loss, minimum echo, distortion, crosstalk, etc.

-there must be an adjustable gain/loss

three types of subscriber loop design

1. normal loop

2. long line

3. special service

________-> least line

_________ -> common. no additional device to extend distance limitation - uses long coil to extend distance but: line cannot be used for internet because it operates at high freq. , loading coil only uses low pass freq. (voice)

special service

normal loop

- used for existing copper line/wire for high speed data transmission

Digital Subscriber Line (DSL)

is a broadband architecture where fiber optic cables run to a nearby street cabinet, and then existing copper wires (usually telephone lines) or coaxial cables complete the connection to homes and businesses.

FTTS (Fiber to the Street)

reference freq. in ph

800 Hz

Broadcast frequency

50 Hz - 15 KHz

subscriber loop length limits

1. attenuation limit

2. signaling limit

-refers to loop AC-loss at refrence frequency measured in dB or Np

-ref. freq. : 1000 Hz (North Am), 800 Hz (Eu, and other countries)

ATTENUATION LIMIT (TRANSMISSION DESIGN CRITERIA)

as a telephone is extended in length, _____________________________

as a telephone is extended in length, its loss at reference frequency increases

as loop extended in length while the battery (supply) voltage is kept constant, the effectiveness of signaling is ultimately lost

SIGNALING LIMIT (RESISTANCE DESIGN CRITERIA)

ATTENUATION LIMIT:

SIGNALING LIMIT:

ATTENUATION LIMIT: FREQUENCY

SIGNALING LIMIT: RESISTANCE

both ______ and ______ are to be considered in determining maximum subscriber loop length/design

resistance and frequency

- in a communication network refers to the aggregate of all user requests being serviced by the network

- traffic engineering alone who is responsible for Grades of Service na ipoprovide

Telephone Traffic

______

-large group of servers are more efficient for it to avoid callers having to wait but is more costlier.

- the rate at which calls arrive is seldom uniform

- alternate route to the destination increase the robustness of the network

principles that govern network design

fundamentals of traffic engineering

1. system

2. magbibigay ng service

3. maghahandle ng load

GRADE OF SERVICE

QUANTITY OF SERVER/TRUNK

TRAFFIC LOAD

is any effort on the part of a traffic source (subscriber, line, selector, etc.) to seize a circuit, switch or other traffic channel, whether or not the attempt is successful)

ATTEMPT

is any actual engagement or seizure of a circuit, switch or other traffic channel.

CALL

is the number of calls per unit of time. In practice, the time unit generally used is the busy hour. Calling rates frequently also designate the sources as, for example busy hour calls per main stations.

CALLING RATE

is the continous 60 minute period of the day during which the highest usage occurs. It does not necessarily coincide with a clock hour such as 9-10 a.m., etc. but may be offset as, for example, 9:15-10:15 a.m

BUSY HOUR

is the ratio of busy hour to total day calls. This is sometimes expressed as LENGTH OF DAY and when so expressed is the reciprocal of the above ratio. Thus, if the call concentration is, say, 0.125, the length of day is 1.00/0.125, or 8 hours.

CALL CONCENTRATION

is the length of time during which a call engages a traffic path or channel. In practice, the holding time will usually differ for each call, and there is no uniform holding time. For engineering purposes the average holding time for a large number of calls, obtained on a sampling basis, is usually employed.

HOLDING TIME

is the total occupied time of circuit, switches, or other traffic paths. It is obtained as the product of calls and the average holding time or those calls. The units in which the holding times are expressed determine the resultant units in which traffic is expressed.

TRAFFIC

NOTE: ■ In some of the literature on traffic, one hour of circuit occupation is designated as a __________. The name "_____" has now been adopted officially (International Standard Unit), to avoid confusion with "Traffic Unit"

"Traffic Unit" (TU)

Erlang

Is the traffic per time unit. In practical traffic calculations, the units usually employed are the CCS and the busy hour, so that traffic density is usually stated in terms of CCS per busy hour, abbreviated BH CCS., For mathematical calculations and development of formulae, it is customary to express traffic in terms of busy hour Erlang (BH ERL), since the use of the Erlang unit simplifies calculations,

TRAFFIC INTENSITY

is the busy hour traffic density per traffic source (subscriber line, selector, etc.) note that there is a difference between calling rate, which is calls per traffic source, and traffic rate, which is density (BH CCS, BH ERL, etc.) per traffic source.

TRAFFIC RATE

is a measure of the probability, that during a specified period of peak traffic a call offered to a group of trunks or circuits will fail to find on Idle circuit at the first attempt. Usually applied to the busy hour of traffic.

GRADE OF SERVICE

Traffic flow formula

A = C (calling rate per hour) x T (the average holding time per call)

The preferred unit of traffic is the Erlang named after the Danish Mathematician, _________. The Erlang is a dimensionless unit.

A.K. Erlang

another unit for traffic unit (TU)

1 ERL = 1 TU = 1 SERVER

other traffic unit that are not dimensionless are as follows:

Call hour (Ch)

Call second (Cs)

is the quantity represents by one 100s call or by aggregate of 100 Cs of traffic.

"Cent" Call-second (CCS)

is the average intensity in one or more traffic paths occupied in the busy hour by 1-2 minutes call or for an aggregate duration of 2 minutes

Equated Busy Hour Call (EBHC)

traffic units can be related as follows:

__ Erlang = __ EHBC = __ CCS = ___ Cmin

1 Erlang = 30 EHBC = 36 CCS = 60 Cmin

1 Erlang is how many servers?

1 server = 1 erlang

___- di ka makaconnect / nasa queue

___- nakakaconnect ka/ naoccupy yung channel

Holding Time

Traffic

- probability that a call will be blocked at first attempt and at busy hours

Grade of Service (GoS)

to convert minutes into erlang you should just ___________

to convert erlang into CCS you should just _______

divide it into 60 mins

multiply it to 36 CCS

typical GOS range: ____________

P01 - P05

Possible way to increase Traffic caused by a group of circuit:

o Queueing (waiting)

o Alternate Routing

Blockage Theories

■ Block Calls Cleared or BCC (Loss probability equation or GOS)

■ Block Calls Delayed (Delay probability equation)

■ Block Calls Held (Loss probability equation)

when blockage is encountered calls overflow and then completed

Block Calls Cleared or BCC (Loss probability equation or GOS)

calls are held in Queue until a server is available and then call is completed

Block Calls Delayed (Delay probability equation)

merely given a fast busy signal or Teoder signal and must redial later

Block Calls Held (Loss probability equation)

formula for Erlang B (BCC)

P = (A^n/n!)/summation of (A^x/x!) from x=0 to n

formula for Erlang C (BCD)

P = (A^n/n!) (n/n-A)/summation of (A^x/x!) + (A^n/n!) (n/n-A) from x=0 to n

formula for Poisson (BCH)

P= (e^-A)(summation of (A^x/x!)

max. frequency: ~1 MHz

max. data rate: Voice only

CATEGORY OF UTP CABLE

Category 1 (Cat 1)

max. frequency: ~4 MHz

max. data rate: 4 Mbps

CATEGORY OF UTP CABLE

Category 2 (Cat 2)

max. frequency: 16 MHz

max. data rate: 10 Mbps (Ethernet)

CATEGORY OF UTP CABLE

Category 3 (Cat 3)

max. frequency: 20 MHz

max. data rate: 16 Mbps

CATEGORY OF UTP CABLE

Category 4 (Cat 4)

max. frequency: 100 MHz

max. data rate: 100 Mbps

CATEGORY OF UTP CABLE

Category 5 (Cat 5)

max. frequency: 100 MHz

max. data rate: 1 Gbps

CATEGORY OF UTP CABLE

Category 5e (Cat 5e)

max. frequency: 250 MHz

max. data rate: 1-10 Gbps (up to 55 m)

CATEGORY OF UTP CABLE

Category 6

max. frequency: 500 MHz

max. data rate: 10 Gbps (up to 100 m)

CATEGORY OF UTP CABLE

Category 6a

max. frequency: 2000 MHz

max. data rate: 25-40 Gbps (short range)

CATEGORY OF UTP CABLE

Category 8

The total energy of a signal in the time domain is equal to the total energy in the frequency domain.

Parseval's Theorem (Energy Theorem)

is like STP, but with an extra outer braided or foil shield similar to coaxial cable as shown in figure 4, which offers still improved protection from interference

from external sources.

S/STP
SCREENED SHIELDED TWISTED PAIR WIRE

parts of coax

A:outer plastic sheath, B:copper screen, C:inner dielectric insulator, D:copper core

RG ___ used in thinnet

RG-58

especially constructed

hollow metallic pipes. they are used at microwave freq.

Waveguides

______ is the power loss of a radio signal as it travels from the transmitter to the receiver.

free space loss

The first artificial satellite, launched by Russia (then known as the

Soviet Union) in the late 1950s, was about the size of a basketball. It did nothing but transmit a simple______ signal over and over.

Morse code

frequency bands used in satellite and radar

Satellites can be

classified according to orbits, in terms of altitude, such as:

the___________can transmit data to many destinations at the same time. The broadcast radio covers the range of frequency

from 3 to 300 Hz. From 30MHz to 1GHz, this range is most effective for broadcast radio to transmit data.

broadcast radio

________ is achieved using transceivers (see figure 9) that modulates non-coherent infrared light. Transceivers must be line of sight to each other, either directly or by reflection from light-colored surface such as the ceiling of the room.

Infrared communication

The infrared part of the electromagnetic spectrum covers the range from roughly 300 GHz (1 mm) to 400 THz (750 nm). It can be divided into three parts:

• Far-infrared
• Mid-infrared

• Near-infrared

_______ is the combination or hybrid of different bounded media of the same type in order to increase the capacity (such as bandwidth and distance) of the

line carrying the information. It provides the capability for handling low speed data communication, high-speed local area network communication, and sometimes

also video signal distribution.

Cabling system

-is a thin, flat electrical conductor separated from a ground plane by a layer of insulation or an air gap

-used in printed

circuit designs

microstrip

-is a conductor sandwiched by dielectric between a pair of ground planes

-like microstrip but sandwiched between two ground planes and respective insulating layers

stripline

is a measure of how far electrical conduction takes place in a conductor, and is a function of frequency.

skin depth

is a graphical calculator. it allows us to see at a glance

what the effects of altering the transmission line (feed)

geometry will be. If used regularly, it gives the practitioner a

really good feel for the behavior of transmission lines and the

wide range of impedance that a transmitter may see for

situations of moderately high mismatch (VSWR).

Smith Chart