3 Types of Telecommunications

• Voice (standard lines)

– analog and digital sets

– Fax

– modems

• Data

– dedicated and switched

• Video

– video phone, Internet, ISDN, DSL, T1, DS1, DS3, CATV, ATM... (Wireless??)

Telecommunications

• Defined as: “the science or technology of communication by telephone, telegraph, etc.”

The Random House College Dictionary, revised edition

• “Using technology to have two way communication over a distance. Whether it is voice, data, or video.” (Gary’s definition)

Definition of Telecommunications continued

• The science of communicating over a distance by telephone, telegraph and radio.

• A means of transmission or reception and the switching of signals, such as electrical or optical, by wire, fiber or electromagnetic transmission through the air.

Definition of Telecommunications continued

• *****Defined as: “is the transmission of information – in the form of voice, data, video, or images, across a distance, over a medium, from a sender to a receiver-in a usable and understandable manner.”

Voice and Data Communications Handbook - Regis Bates

Telephones

• “We use this service eight times per day, on the average. With this service, emergency aid can be quickly summoned, airline reservations made, goods ordered and purchased, and funds transferred. No special skills are needed to use this service. This ubiquitous service that totally penetrates our lives is the telephone.

~110 Years in service

• Telephone service is truly synonymous with communication, but is so taken for granted that we frequently forget its paramount position in our lives and society.”

• Noll, A. Michael. “Introduction to telephones and Telephone Systems.” Boston. Artech House, 1998

Telephone Networks

• Telephones

• Transmission media

• Switching

• Signaling to control everything

Basics of a Telephone network

1. Station apparatus• 2500 set

• Digital set

• What else?

2. Transmission media• CO, DID, T1, DS3, what else?

3. Switching• PBX, Central office, long distance

4. Controlling the network

(signal that tell the equipment where to route the calls)

Definition of sound

• Sound is also a type of wave that we cannot see. Like ocean waves, sound waves something to travel through like waves through the ocean or through a flag. Sound can travel through air because air is made of molecules. These molecules carry the sound waves by bumping into each other, like dominoes knocking each other over. Sound can travel through anything made of molecules - even water! There is no sound in space because there are no molecules there to transmit the sound waves. C/O:

• http://science.hq.nasa.gov/kids/imagers/ems/waves.html

Bandwidth

• Definition of bandwidth: The width of the frequencies that comprises a signal or; the French mathematician Fourier: “any complex waveform can be decomposed into the sum of pure tones, or sine waves, at different frequencies and with different maximum, amplitudes and phases. A graphical plot of the frequencies that comprise a signal, or that are passed by a communication channel, is called the spectrum.”

Voice Bandwidth• Each telephone speech signal occupies a

frequency spectrum from about 300 to 3,300 Hz (Hertz / cycles per second).

• Typically know as a 3Khz bandwidth for voice.

Behind the scenes

• Transmission, switching and signaling– Local loop– Central office to a POP – POP to Toll network– Trunking– Toll network to POP– POP to CO – Destination

Local Loop

• Simply defined: The pair of wires running from your home (premise) to the local telephone company (CO or central office).– CPE to -– intra-premise wiring to -

• Demark– Protector block ( fuses, spark gaps ) to -– Local loop (pair of wires running back to the

CO)

Basics on Wiring within a facility

• Incoming lines from the CO to the PBX (demark)– CO

– DID

– PRI

– DS1

• PBX to the individual stations

• Wiring center’s purpose

Local Exchange Carrier

• LECs– ? Who is your telephone company?– What services do they provide?

• Dial tone

• Calling features

• Access to IXCs

• What else??

• They provide intra-Lata service

Competition to the LECs

• Effects on costs?

• What about service from the competition?

• What about high volume calls versus low volume calls?

IXC’s or Interexchange Carriers

• These are the long distance companies ie: AT&T, MCI, Sprint…

• They provide long distance service across

Latas or Inter-lata service

Pre 1984 network hierarchy

• Vertical monopoly– Management– R & D– Manufacturing– Local service– Long distance

Post 1984

• 7 Baby Bells

• Which one are we in??

• How many remain today?

Wikapedia’s current map

Was divestiture a good thing or not?

• Opinions?

• Teleco reps reactions during the 80’s

• Quality of service issues

• Who uses which long distance provider?

• The state’s STS system

• UW’s use STS

• FVTC’s long distance provider

POP

• POP stands for Point of Presence

• Page 15, The place where the IXC (inter-exchange carrier / long distance provider) connects to the LEC (Local exchange carrier / CO).

North America numbering plan

• “Under the stipulations of the MFJ (Modified Final Judgment), the United States was divided into 160 local access and transport areas (LATAs)”

• Bell operating companies could provide service within LATAs but not across LATAs (not inter-LATA services)

LATAs

• LATAs basically provided a line of demarcation between local service provider and major long distance providers.

• AT&T among others, provide long distance services from LATA to LATA

• Local telephone companies provide service within the LATAs

Reading assignment – Finish reading Chapter 1

• Subject – Electronic Communications