CHAPTER FIVE: PART TWO

1
CHAPTER FIVE PART TWO

• PRIVATE TELEPHONE SYSTEMS

2
KEY SYSTEMS

• KEY SYSTEMS ARE SMALL PRIVATE TELEPHONE SYSTEMS
• EACH TELEPHONE CAN ACCESS TWO OR MORE LINES
• EACH SYSTEM CAN HANDLE FOM 3 TO 50 LINES
• LARGEST AND FASTEST GROWING SEGMENT OF MARKET DUE
  TO SMALL BUSINESS NEEDS

3
THE PBX

• PBX PRIVATE BRANCH EXCHANGE, ALSO KNOWN AS PABX
  (PRIVATE AUTOMATIC BRANCH EXCHANGE AND CBX
  (COMPUTER BRANCH EXCHANGE)
• 50 TO 10,000 TELEPHONES
• SIMILAR IN CAPACITY AND CAPABILITY TO TELEPHONE
  COMPANY EQUIPMENT
• LOCATED ON BUSINESS PREMISE

4
PBX FEATURES
FEATURES ARE DETAILED ON 201 TO 205 OF TEXTBOOK
AS WITH COMPUTERS SECURITY IS A GREAT CONCERN
5
CENTRIX SERVICE

• SIMILAR TO PBX BUT EQUIPMENT IS OWNED BY PHONE
  COMPANY AND LOCATED AT CENTRAL SWITCHING OFFICE

6
PRIVATE VOICE NETWORKS

• PBXS OR KEY SYSTEMS AT SEVERAL LOCATIONS ARE
  TIED TOGETHER THROUGH LEASED LINES TO CREATE A
  PRIVATE PHONE SYSTEM
• LEASED LINES ARE CALLED TIE LINES OR TIE
  TRUNKS
• MAY BE A VIRTUAL NETWORK COMPOSED OF STANDARD
  TELEPHONE COMPANY EQUIPMENT
• SPECIAL FEATURES MAY INCLUDE AUDIO
  TELECONFERENCING AND VOICE MAIL

7
WIRELESS COMMUNICATIONS

• FASTEST GROWING SEGMENT OF VOICE COMM.
• CORDLESS TELEPHONES
• ANALOG VERSIONS ARE NOT SECURE AS THEY
  BROADCAST THE CALL
• DIGITAL VERSIONS MORE SECURE DUE TO SPREAD
  SPECTRUM OR JUMPING BETWEEN FREQUENCIES
• CELLULAR TELEPHONES
• ORIGINALLY CITIES, NOW NATIONALLY DIVIDED INTO
  CELLS
• MTSO MOBILE TELEPHONE SWITCHING OFFICE(CENTRAL
  OFFICE EQUIVALENT)

8
CELL PHONE LAYOUT
9
THIS COULD BE YOU
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CELL PHONE CALL STRUCTURE
MONITORS CALLS AND SWITCHES BETWEEN CELLS
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TYPES OF CELL PHONE TRANSMISSIONS

• TDMA TIME DIVISION MULTIPLE ACCESS DIVIDES
  RADIO FREQUENCIES INTO SEPARATE CHANNELS AND
  ASSIGNS ONE TO YOUR CALL
• MOST USED IN US
• GSM GLOBAL SYSTEM FOR MOBILE COMMUNICATIOMNS IS
  BASED ON TDMA BUT SUPPORTS BOTH VOICE AND DATA
• THE STANDARD IN EUROPE AND ASIA
• CDMA CODE DIVISION MULTIPLE ACCESS BROADCAST
  ALL CALLS WITHIN THE SAME CHANNEL
• SUPPORTS VOICE AND DATA AND IS THE BEST

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CELL PHONE CONCERNS

• CONCERN OVER RADIATION HAZARD
• MOTORIST USING CELL PHONES
• NOT SECURE AS CONVENTIONAL PHONES

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OTHER MOBILE USES

• INTERNET ACCESS WITH I-MODE
• REFER TO SIDEBAR 5-1 ON PAGE 219
• MARINE TELEPHONE SERVICE
• TRANSCIEVER ON BOAT TO TRANSCIEVER ON SHORE
  HOOKED INTO PUBLIC SYSTEM
• AERONAUTICAL TELEPHONE SERVICE
• TRANSCIEVER ON PLANE TO TRANSCIEVER ON LAND
  HOOKED INTO PUBLIC SYSTEM
• AS PLANE MOVES CALL MUST BE SWITCHED FROM SITE TO
  SITE