Principles of Voice & Data Lesson 1: Telephony Essentials Bellevue Community College Bob Young, Instructor
Terms & Explanations PSTN Public Switched Telephone Network
Terms & Explanations POTS "Plain Old Telephone Service" as in, "POTS line."
Terms & Explanations Phone Parts Transmitter - Mouthpiece Receiver - Earpiece
Terms & Explanations Full Duplex - voice can be sent in both directions at the same time. Half Duplex - voice can be sent in one direction at a time.
Terms & Explanations C.O. or CO Central Office
Terms & Explanations CPE Customer Premise Equipment CPE may be owned by the telco or by the customer
Terms & Explanations The "Last Mile" From the CO to the CPE
Terms & Explanations Outside Plant Telco equipment between the CO and the customer Poles, lines, vaults, etc.
Terms & Explanations On Hook The phone's handset is in the cradle. Open loop condition - no loop current.
Terms & Explanations Off Hook The phone's handset is out of the cradle. Closed loop condition - loop current is present.
Terms & Explanations RBOC Regional Bell Operating Company Divestiture of AT&T Formation of 7 RBOC's
The Seven RBOCS: 1)Ameritech 2)Bell Atlantic 3)BellSouth 4)NYNEX 5)Pacific Bell 6)Southwestern Bell 7)US WEST
RBOC Map, 1984
Terms & Explanations BOC Bell Operating Company Smaller, regional companies within the RBOC's – (22 BOC's)
Terms & Explanations IXC Interexchange Carrier After divestiture, IXC's handled long distance calls
Terms & Explanations LEC Local Exchange Carrier
Terms & Explanations LATA Local Access and Transport Area
Terms & Explanations ILEC Incumbent Local Exchange Carrier
Terms & Explanations CLEC Competing (or Competitive) Local Exchange Carrier
Terms & Explanations British Terms GPO - General Post Office BPO - British Post Office BT - British Telecom
Terms & Explanations ITU International Telecommunications Union
Terms & Explanations ITU-T International Telecommunications Union - Telecommunications Standardization Sector
Terms & Explanations Tandem Office A central office unit used primarily as an intermediate switching point for traffic between local central offices within the tandem area
Terms & Explanations Toll Tandem A central office unit used as the switching point between local CO traffic and toll (long distance) traffic
Terms & Explanations EO End Office A Central Office that connects directly to subscribers
Terms & Explanations Switches - Class 5 An End Office switch Provides local loop connections Call signaling and control - setup and knockdown
Terms & Explanations Switches - Class 4 A tandem switch Capable of connecting Class 5 switches
Terms & Explanations Switches - Class 3 A toll traffic switch Connects LEC's Capable of connecting Class 4 & 5 switches
Terms & Explanations PCM Pulse Code Modulation -law (North America & Japan) A-law (all other countries) 8 KHz sampling rate
Terms & Explanations PCM Issues Unrepresentative Sample Lack of Information Too Much Information
Terms & Explanations POP, PoP Point of Presence POI Point of Interconnection
Terms & Explanations FX Foreign Exchange FXO - Foreign Exchange Office FXS - Foreign Exchange Station
Terms & Explanations PBX Private Branch Exchange
Terms & Explanations KSU Key Service Unit or Key Switching Unit
Terms & Explanations DID Direct Inward Dialing as in, "DID Trunk"
Terms & Explanations DOD Direct Outward Dialing as in, "DOD Trunk"
Terms & Explanations Centrex Service A telco service in which the PBX hardware and functionality is provided and maintained by the telco
Terms & Explanations Analog Loop Start The call is originated by going off hook. Loop current initiates the call sequence.
Terms & Explanations E & M Trunks Voice and signaling are carried on separate wires E = "Ear" M = "Mouth"
Terms & Explanations Ground-Start Trunks The call sequence is initiated by grounding either the tip (from CO) or the ring wire (from PBX)
Terms & Explanations DSH Digital Signal Hierarchy DS0, DS1, DS3 T1, T3 T1 = Mbps
Terms & Explanations SF & ESF Super Frame (D4) Extended Super Frame
Terms & Explanations E-Carrier Europe uses E1's instead of T1's E1 = Mbps
Terms & Explanations SONET Synchronous Optical Network North American Standard Compare with SDH STS-1 = Mbps
Terms & Explanations STS & OC Synchronous Transport Signal Optical Carrier Exact same data rates Know both terms
Terms & Explanations STS-1 = OC-1 = Mbps STS-2 = OC-2 = Mbps STS-3 = OC-3 = Mbps etc.
SONET Physical Hierarchy
SONET Architecture
SONET Ring
Terms & Explanations SONET & OSI Model OSI Layer 1 Standard (Physical Layer)
Terms & Explanations More SONET Info SONET can be used for: ATM Gigabit Ethernet
Terms & Explanations SDH Synchronous Digital Hierarchy International Standard Don't confuse with DSH STM-1 = Mbps
Terms & Explanations Mbps STS-3 OC-3 STM-1
Terms & Explanations A & B Bit Signaling Digital equivalent of analog line signals Status of bits indicates idle or busy (on-hook, off-hook)
Stratum Clocks
Terms & Explanations Types of Timing Asynchronous Synchronous Plesiosynchronous
Terms & Explanations CSU/DSU Channel Service Unit Data Service Unit
Terms & Explanations SWC, WC Service Wire Center Wire Center
Terms & Explanations Distribution Frame Permanent wiring set up for easy cross connection
Terms & Explanations MDF Main Distribution Frame Typically at CO or large PBX
Terms & Explanations IDF Intermediate Distribution Frame Typically outside plant or customer premise
Terms & Explanations CDF Combined Distribution Frame Vertical blocks - CO lines Horizontal blocks - inside lines
Terms & Explanations MPOE Minimum Point of Entry Demarcation Point (Demarc)
Terms & Explanations NID Network Interface Device
Terms & Explanations Load Coils Reduces line loss Matches impedance Analog circuits only - Can't use in digital circuits
Terms & Explanations Bridge Tap Allows a cable to be run to more than one location Each circuit can only be used at one location
Terms & Explanations Call Processing Call setup Call maintenance Call completion (knockdown)
Call Signaling Dial tone Hz and 440 Hz at –12 dBm Pulse dialing - (10 pps standard) 40msec make, 60msec break, 600msec pause DTMF - (23 pps standard) Ring - (80-90 VAC at 20 Hz) Ringback Hz and 480 Hz at –20dBm, 0.2 sec on, 0.4 sec off Busy Hz and 620 Hz, 0.5 sec on, 0.5 sec off
Analog Problems Loss Echo Noise Crosstalk Delay
Terms & Explanations Echo Cancellation Acoustic Echo Control (wireless networks) Far End Echo Cancellation (long distance, satellite)