telephone /voip
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www.convergencetechnologycenter.org DUE 402356
Telephone /VoIP
Learning Activity 4
Learning Outcomes 1 and 5
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Telephony / VoIP
Differentiate and describe POTS vs. VoIP delivery.
Identify and troubleshoot common issues.
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Telephony / VoIP
Analog
1. Plain Old Telephone Service (POTS)
2. Most home telephones still use analog devices connected to analog phone lines
3. Signals move relatively slowly when carried in physical media such as copper wire and cable
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Telephone Subsystem
Delivers telephone services to home Design follows local codes and standards Demarcation
Telephone enters home Service distributed to home SP responsibility stops
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Low-Voltage
Telephone Cat 3
FCC required minimum for phone lines Older homes
Cat 5 Newer constructions Recommended by ANSI/TIA/EIA-570-A
Scalable Expanded for VoIP
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Tip and Ring
Early telephone Switchboard plugs inserted into receptacle
Tip of plug = 1 conductor Ring = other conductor “Tip and Ring”
Colors of Tip White Red Black Yellow Violet
Colors of Ring Blue Orange Green Brown
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Wire Pairs and Color Codes 4 Pair cable such as CAT 5
Primary color is tip = white with tracer White wire = tip = first wire of pair to be punched down
Ring = Solid color Wire Pairs
Pair 1 - Blue White/Blue Blue
Pair 2 - Orange White/Orange Orange
Pair 3 – Green White/Green Green
Pair 4 White/Brown Brown
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Telephony / VoIP
Frequency Division Multiplexing
1. The process of allowing analog lines the capability to carry multiple conversations or data streams at the same time.
2. Made possible by dividing analog frequencies on a line and sharing them among different voice and data lines
3. Multiple telephone lines are possible on home and businesses without the additional cost of adding more wires.
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Telephony / VoIP
Centrex System
Central Switching Exchange, used by organizations having telephones in many locations
A telephone line would have many extensions, but only one call could be made at a time.
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Telephony / VoIP
VoIP Data (Packets) are moved via Internet Protocol (IP) from LAN to LAN.
Voice can travel on same LAN network.
Systems require special hardware, configuration and settings in quality to meet the same standards set forth by the Telephone System.
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Telephony / VoIP
Voice over IP (VoIP)
Packets must be received and reassembled into the order they were sent, voice decoded from digital to analog and sent to the phone speaker, all without any time lags or delays.
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Telephony / VoIP
Digital
Faster data/voice transfer rates
Packets are used as the transport of digital signals
Use Protocols to set standards, … i. e. Addressing, Errors, Control
Uses zeros and ones, making it easy to read and duplicate
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Telephony / VoIP
Soft phonesAn application (software) written to act as a telephone with a computer. The soft phone:
Displays phone features
Hold Button
Caller ID
Message waiting light
Other features
Routes calls with use of a headset or special (USB) phone connection
Works with minimum PC hardware requirements
Provides same functionality as the PC. (Remote, mobility)
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Telephony / VoIP
POTS
1. Cross talk
2. Radio interference
3. Dead ports
4. REN (Ringer Equivalence Number)
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Telephony / VoIP
Crosstalk:
..speech or signaling tones leaking from other people's connections
..a signal affecting another nearby signal
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Telephony / VoIP
Radio Interference:
..disturbance caused in a radio receiver or other electrical circuit by electromagnetic radiation emitted from an external source
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Telephony / VoIP
Ringer Equivalence Number (REN)..a somewhat arbitrary number which denotes the electrical load a telephone ringer has on the line
REN – in the US considered a yardstick
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Telephony / VoIP
PBX
Private Lines Switch System
Usually is considered the demarcation point or demark between the owner and the Telephone Company.
A device used to route calls from the owners equipment (PBX) to the public telephone system
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Telephony / VoIP Describe and define fundamentals of
telephone systems
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Troubleshooting
Steps to troubleshoot problems Observe symptoms Isolate cause Check connections Test hardware Test software
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Troubleshooting Telephones
Possible Telephone problems: Inconsistent ringing of phone,
Can not hear / or be heard,
Dialing wrong number
Solutions: The handset, the telephone base, wiring, or Telephone Co. (software)
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Troubleshooting Telephones
Solutions:
-- Make sure phone is working,
-- Connect in several phone jacks
-- Check for a dial tone
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Troubleshooting Telephones
Power Limits: The phone has a limited amount of power available from the phone company to make your phones ring
Solution: Exceeded REN - Remove a phone.
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Troubleshooting VoIP
VoIP – Telephones
The phone does not work.
Solution:
No Power No IP address Software issues
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Telephone vs. VoIP: Summary
o The Analog Telephone System (POTS) has been in existence for over 130 years.
o Digital Telephone Transmission has improved voice quality and added other special features.
o The Public Switched Telephone Network provided a central exchange of connecting private networks to the public network.
o Digital Telephone transmission is being expanded into the Internet as VoIP.
o The analog telephone is still used in many households.o The analog telephone is a voice device with a speaker, microphone,
and digital keypad.
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Telephone vs. VoIP: Summary
Telephone: Old Technology Reliable Good Sound Quality Relative Inexpensive
VoIP: New Technology Becoming popular
Many added features Lower cost
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Questions and Contacts
Julian Carranza, jcarranza@dcccd.edu Eliazar Martinez, emartinez@dcccd.edu
This material is based upon work supported by the National Science Foundation underGrant No. 0402356. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
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