MAS 102 Midterm exam study guide 3: Principles of Telephony
Key Telephone Systems:
For the small business user, Permits multiple lines to terminate on one telephone with the punch of a button, Many features are inherent in the system, such as hold and call pickup
The Telephone has five parts
Transmitter Receiver Ringer Control unit Switchhook
International Telecommunications Union Is a
United Nations Agency
There are four primary types of data communications
Voice, data, message, and image
Transmitter
a microphone
Receiver
a speaker
Every telephone line is
a twisted pair of wires (2X)
Ringer
bells, whistles, horns, buzzers, and musical interludes
During times of unusually high use, central offices may be overwhelmed -- this results in
blocking
2X wires connect phones to a
central office
Switching
connecting one circuit to another
Analog Transmission is a
continuous and continuously varying flow of electrical energy that varies with the frequency and strength of the sound
Rotary phones used
dial pulsing signaling
Cellular may be analog or digital, but is primarily
digital since 1997-98
what came after step-by-step system (10,000 users) and panel system (30,000 users)
electronic switching systems, Minimum of 100,000 lines
Single-Line Systems Consist of an
individual line and one or more telephones each line can support several extensions may be residential or small business, but business charges are higher largest market for phone business
Only basic black phones were available until the
late 50s
Each central office serves a
specific geographic area, size depends on the number of lines
Digital Transmission is a
stream of discrete on and off pulses called bits
The central office began as a
switching center
Mathematically no more than
8 million numbers per area code
Cordless Phones
Base station connected to phone line and cordless handset Uses low-power radio transmission Absolutely no expectations for privacy
local loop consist of three parts
Drop wire -- from house to pole to a: Distribution cable -- runs down your street on poles to a: Feeder cable -- connects to the central office
Push-button phones use
Dual Tone Multifrequency
Personal Communications Systems (PCS) are digital
services May be a satellite-based service
Push-button phones are
Necessary for "talking" to computers
Digital transmission is better quality because
No noise and distortion More efficient and faster More economical in the long run
Private Branch Exchanges (PBX)
On-premises computer-based switching system for large organizations Calls between stations are dialed directly, usually with a single-digit prefix Can be purchased, leased, or rented from AT&T, RBOCs and many other vendors
Central Offices
Originally, every phone went from one phone directly to another As the number of phones increased, this became unworkable, plus: Telephones were more valuable if they connected to multiple phones
The Telephone is
The basic instrument of all communications technology
Transmission of Sound
Sound waves are converted to electrical energy, Transmitted over wires or another medium, Converted back to sound, Transmission is an analog signal, Frequency range is from 300 to 3,400 Hz
Voice communication is
Telephony
Switchhook
signals the phone company and caller that the phone is either idle or in use
Trunk lines connect
one central office to another
The central office provides links to
other central offices and to long distance providers
other kinds of communications make heavy use of
phone lines
Control unit
push buttons or rotary dial
Electricity for the phone is delivered via
the 2X wire
Automatic exchanges began to replace operators in
the early 20s
The ITU-T established
world-wide numbering plan
