Study Sheet Flashcards
What is sound?
Audible frequencies created by a source such as a person talking.
A periodic variation in air pressure.
travels in form of sound waves
types of sound waves
Pressure waves that vibrate molecules in a medium such as the air.
high frequency vs low frequency
loud vs soft (amplitude)
pleasant vs noise
frequency
number of cycles per second
Number of events happening over a defined time period.
wavelength
length of the waveform
The length of one complete waveform. The higher the frequency, the shorter the wavelength; and the lower the frequency, the longer the wavelength.
what is a decibel used for
unit used to measure signal strength
used on a logarithmic scale
convert decibels to milliwatts
10 milliwatts equals how many decibels
100 milliwatts equals how many decibels
10mw = 10dbm
100mw = 20 dbm
milli watts on the x axis and decibels on the y
to double a milliwat is how many decibels
3
human ear can hear from qhat decibel to what decibel
0-120
formula to convert power to decibels
Decibels (dB) = 10 log(P2/P1)
P1 is reference and P2 is output
frequency of human hearing
20 Hz
20,000Hz
20kHz
frequency of human speech
400 hz
4,000 hz
4khz
local loop
subscriber loop consisting of twisted pair connecting each phone to local exchange.
has both DC and AC power
ADSL
Asynchrnous Digital Subscriber Line
used for internet access on same wires
local exchange office does what
provides power to telephone circuits
dial tone
ring signal
other info and billing tracking
circuitry for routing
ringing voltage
90 VAC at 20 hz
where do telephones enter home business
demarcation point
subscriber interface
LEC
local exchange carrier
local companies that provide phone service
LATA
local area and transport network
geographic regions
POP
point of presence office for that compnay in a LATA
trunks for long distance carriers are called
IXC;s
inter exchange carrier
IXC
interexchange carrier
what is DTMF
Dual Tone Multi Frequencey
used for dialing and sending the number input as a frequency to the central office
Steps of Analog to Digital conversion
Sampling-8000 times
Quanitizing: compares to 255 level scale
Encoding: Translating PAM sample into PCM word converted into bipolar signal and multiplexed into DS-1
digital modulation techniques
ASK-amplitude FSK-frequencey PSK-phase shift QAM-quadrature amplitude PCM-pulse code modulation
PCM
pulse code modulation is used for converting in todays modems
B8ZS
binary 8 zero binary 8 substitute
8 zeros are converted to a special bit pattern that is a bipolar violation due to FCC rules
AMI
alternate mark inversion not widely used replaced by B8Zs
FDM
Frequncey Division Multiplexing
puts different frequenceys on one signal
TDM
time division multiplexing
puts digital words into time slots in one signal
another name for channel
DS-0
how many DS-0 in DS-1
24
How may DS-1 in a DS-3
28
How many DC-3 in OC 48
48..what ever the number is thats how many DC-3’s
whats the name of the multiplexer turning DS-1 into DS-3
M13 Multiplexer
channel banks
convert DS0 into DS1
DS3 bandwidth
45 MBps
DS-0 bandwidth
64kp
DS-3 cable is
coax or fiber
DS-3 can also be sent overe
microwave…3 per channel
DS-3 framing formats
M13
C bit parity
Unchannelized
SONET is
synchrnous opitcal network
Sonet frames are similar to TDM protocols
relies on external clock and not timing bits
4 types of fast packet multiplexing
Statistcal fast packet
Asynchrnous Transfer Mode ATM-multiplexes fixed length cells
Frame Relay-multiplexes variable length packets
IP…multiplexes variable length packets
DWDM
dense wave divsion multiplexing is multiplexing for fiber optic systems
4 types of transmissino modes
serial-one bit after other
parrallel-bits across multiple conductos
asycnhrnous-start and stop bits to define frames
synchrnous-clock source to synch frames
SS7
signaling system 7….
out of band signaling used to SETUP calls
Trunk
circuit shared by multiple users that CONNECTS SWITCHES
Tandem switch
switch connected to other switches
CLEC vs ILEC
competetive local exchange carrier
Incumbent local exchange carrier
feature group trunk
trunk used to connect LONG DISTANCE to LOCAL switches
IMT
inter-machine trunks
what kind of switch switches international calls
gateway switch
most common network
T1 or DS1 same thing
LEvels of switches
Class 5-local
Class 4-Tandem
Class3-LD switch
international gateway switch
