Telephone Instruments & Signals Flashcards
The process of conveying information from one place to another
Communication
A long distance communications;
‘tele’ Greek word for distant or afar
Telecommunication
One of the most remarkable devices ever invented
Telephone
Anyone who uses a telephone or data modem on a telephone circuit is part of a global communications network called __
Public telephone network or PTN
The PTN is comprised of several vry large corp. and hundreds of smaller independent companies referred to as _____
Telco
Inventor of telephone
Alexander Graham Bell and Thomas A Watson
Referred to as the Bell Telephone System or “Ma Bell”
AT&T –American Telephone & Telegraph Company
World’s most complicated machine
Bell System
Simplest and most straightforward form of telephone service
POTS – Plain Old Telephone Service
Most fundamental component of a telephone circuit
Local Loop
Provides the means to connect telephone set of the subscriber’s location to the closest telephone office
Subscriber Loop
Telephone office also called ___
end office
local exchange
central office
Enables the subscriber to access the PTN once in the central office
electronic switching system (ESS)
An apparatus for reproducing sound, especially that of the human voice (speech) at a great distance by means of electricity; consisting of transmitting & receiving instruments connected by a line or wire which conveys the electric current
Telephone
Simple analog transceiver designed for converting speech of acoustical signals to electrical signals
Basic Telephone Set
First telephone set that combined a transmitter and receiver into single handheld unit
Butterstamp Telephone (1878)
Introduced by western electric company also called the bell system
Rotary Dial Telephone
Is called a 2500-type telephone circuit
Touch-tone Telephone
Quality of transmission over a telephone connection depends on ___
received volume
Frequency response of the telephone circuit
Degree of the interference
Wires on the local loop
Tip (ground) and Ring (-48 Vdc)
Third wire to be used in a local loop is called ____
Sleeve
A dc voltage is used rather than ac because:
- to prevent power supply hum
- to allow service to continue in the event of a power outage
- people are afraid of ac
the only voltage required for the operation of a standard telephone
48 Vdc
An Electronic oscilllator used to alert the destination party of the incoming calls
Ringer Circuit
Sometimes called switch hook; Simple single throw-double-pole STDP switch
On/Off Hook Circuit
Placed across the ‘tip’ and ‘ring’
On/Off Hook Circuit
idle, open switch
On Hook
in use, closed switch
Off Hook
Combination of passive components (resistors & capacitors)
Use to regulate the amplitude & frequency response of the voice signals
Equalizer circuit
Receiver for the telephone
Speaker
Converts electrical signals received from the local loop to acoustical signals (sound waves)
Speaker
Transmitter for the telephone
Microphone
Converts acoustical signals in the form of sound pressure waves from the caller to electrical signals
Microphone
Also called Hybrid coil or duplex coil
Hybrid network
A Special balanced transformer used to convert 2-wire (local loop) circuit into 4-wire (telephone set) circuit
Hybrid network
Enables the subscriber to output signals representing digits
Dialing Circuit
Are acknowledgement & status signals that ensure the processes necessary to set-up and terminate a telephone call are completed in an orderly & timely manner
Call Progress Tones & Signals
exchange of signaling message over local loops between stations & tel. company switching machines
Station signaling
exchange of signaling message bet. switching machines
Interoffice signaling
Indicate request for service
Alerting Signals
Provide call status information
Supervising Signals
Provide information in the form of announcement
Controlling Signals
Provide routing information (calling & called numbers)
Addressing Signals
is an audible signal comprised of 2 frequencies – 350 & 440Hz
Dial Tone
Each digit is represented by the linear addition of two frequencies
Dual tone multifrequency tones (touch tones)
Used to transfer digits & control signals between telephone sets & local switching machines
Dual tone multifrequency tones (touch tones)
Combination of two frequencies that fall within the same speech BW so that they can be propagated over the same circuits as voice (in-band signaling)
Multifrequency tones
Used to transfer digits and control signals between switching machines
Multifrequency tones
Used to indicate the beginning of a sequence of MF digits
KP
used to indicate the end sequence of dialed digits
ST
Sent from the switching machine back to the calling station whenever the called tel # is off hook
0.5s ON, 0.5s OFF
Station Busy
Congestion tone or no circuit available tone
0.2s ON, 0.3s OFF
Equipment Busy
20 Hz, 90 Vrms
‘on’ for 2 sec
‘off’ for 4 sec
Ringing Signal
440 Hz & 480 Hz
‘on’ for 2 sec
‘off’ for 4 sec
Ring Back
Non-Essential Signaling & Call Progress Tones
- Call waiting tones
- Hold
- Stutter dial tone (for voice mail)
- Calling card service tone
- Intrusion tones
Sound in motion
Speech
Acoustic waves or ___ have no electrical component
Sound waves
Is an apparatus that creates an exact likeness of sound waves with an electric current
Telephone Set
Is a series of telephone connection interfaces (receptacle and plug) that are registered with the US federal communications commission (FCC).
RJ or Registered Jacks
Is a method originally used to transfer digits from a telephone set to the local switch. Also called rotary dial pulsing
Dial Pulses
Occurs whenever the system is overloaded and more calls are being placed than can be completed
Blocking
