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26 Cards in this Set
- Front
- Back
What are the 3 steps for converting analog signal to PCM format?
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-filtering- filters over 4000 hz
-sampling- sample at 8000/sec -digitizing-digitze the sample and put it into binary |
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PBXs and Switches- which one private and public?
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PBX is private and switches are public
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Local Loops
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-provide physical cabling between central office and home
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Phone Lines
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-communication between central office switch and home
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Station Lines
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-interconnect PBX and telephones
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Trunks
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Tie trunks -interconnect PBXs
CO trunks -central office trunks PSTN switch trunks- interconnect central office switches |
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What are the 2 types of Basic Telephony Signaling
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-subscriber signaling- between PSTN switch and subscriber
-trunk signaling- between PSTN switches, between a PSTN switch and PBX, or between PBX switches |
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Name the 2 types of subscriber signaling.
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-loop start- residential, simplest
-ground start- modification of loop start, for PBX loops |
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Name the one type of trunk signaling.
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-E&M- recieve and transmit (between PBX)
-5 types of signaling -separate paths for voice and signaling |
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CAS and CCS Signaling
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-channel associated signaling- signal for call setup in the same channel as a voice call
-exampples TI, DTMF dual tone multi frequency |
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CCS
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Commone channel signaling- separate channel for call setup
-E1, ISDN, DPNSS (Digital private networking signaling system) -QSIG (Q signaling) -SS7 (Signaling System 7) |
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Voice Coding and Compression
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-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 |
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Codec Mean Opinion Score (MOS)
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-compression used during Codec Rate
-offers certain quality of speech |
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What is voice communication a mix of?
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-contorl signaling
-voice conversation |
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What does voice control signaling require?
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-reliable transport provided by TCP/IP
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What does voice conversation transport based on?
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-connectionless UDP/IP
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What are some sources of fixed delay?
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-propogation delay
-sterlization delay -processing delay |
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What are some sources of variable delay
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-queuing delay
-dejitter buffers -variable packet sizes |
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What are some QoS mechanisms?
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-bandwidth reduction
-bandwidth reservation -QoS classification -Congestion management -Congestion avoidance |
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What are some congestion management QoS Mechanisms?
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-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 |
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On Net Calling
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-used to call private tie lines whenever possible
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Off Net Calling- when is it used?
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-when private lines are congested
-if called party is not reachable over the private network -if user manually selects an off net extension |
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Grade of Service (GOS)
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probability of calling being blocked at the busiest hour
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Erlang
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used to calculate the GOS
-equals one full hour of conversation |
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Centum Call Seconds (CCS)
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Erlang/36
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One erlang equals;
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3600 seconds of telephone seconds
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