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26 Cards in this Set

  • Front
  • Back
What are the 3 steps for converting analog signal to PCM format?
-filtering- filters over 4000 hz
-sampling- sample at 8000/sec
-digitizing-digitze the sample and put it into binary
PBXs and Switches- which one private and public?
PBX is private and switches are public
Local Loops
-provide physical cabling between central office and home
Phone Lines
-communication between central office switch and home
Station Lines
-interconnect PBX and telephones
Tie trunks -interconnect PBXs
CO trunks -central office trunks
PSTN switch trunks- interconnect central office switches
What are the 2 types of Basic Telephony Signaling
-subscriber signaling- between PSTN switch and subscriber

-trunk signaling- between PSTN switches, between a PSTN switch and PBX, or between PBX switches
Name the 2 types of subscriber signaling.
-loop start- residential, simplest

-ground start- modification of loop start, for PBX loops
Name the one type of trunk signaling.
-E&M- recieve and transmit (between PBX)
-5 types of signaling
-separate paths for voice and signaling
CAS and CCS Signaling
-channel associated signaling- signal for call setup in the same channel as a voice call

-exampples TI, DTMF dual tone multi frequency
Commone channel signaling- separate channel for call setup

-E1, ISDN, DPNSS (Digital private networking signaling system)
-QSIG (Q signaling)
-SS7 (Signaling System 7)
Voice Coding and Compression
-Pulse Code Modulation (PCM) used i traditional networks is wasteful
-uses 64 kpbs og bandwidth per call
-reduces amount of traffic
-hgher the compression the worst quality of voice,
-voice coding standard is CODE
Codec Mean Opinion Score (MOS)
-compression used during Codec Rate
-offers certain quality of speech
What is voice communication a mix of?
-contorl signaling
-voice conversation
What does voice control signaling require?
-reliable transport provided by TCP/IP
What does voice conversation transport based on?
-connectionless UDP/IP
What are some sources of fixed delay?
-propogation delay
-sterlization delay
-processing delay
What are some sources of variable delay
-queuing delay
-dejitter buffers
-variable packet sizes
What are some QoS mechanisms?
-bandwidth reduction
-bandwidth reservation
-QoS classification
-Congestion management
-Congestion avoidance
What are some congestion management QoS Mechanisms?
-IP RTP Priority- voice identified by RTP port #'s classified into PQ
-PQ- 4 buckets
-CQ- 16 buckets
-WQ- divides bandwidht across queues
-CBWFQ- divided bandwidh on defined weights and classes with no strict PQ avaliable
-LLQ- fair queuing with guarnteed bandwidth with strick prioirty queuing avaailable for voice traffic
On Net Calling
-used to call private tie lines whenever possible
Off Net Calling- when is it used?
-when private lines are congested
-if called party is not reachable over the private network
-if user manually selects an off net extension
Grade of Service (GOS)
probability of calling being blocked at the busiest hour
used to calculate the GOS
-equals one full hour of conversation
Centum Call Seconds (CCS)
One erlang equals;
3600 seconds of telephone seconds