block 6 1A telephony fundamentals Flashcards
What are the voltages the PSTN phone switch utilize and what are they used for?
-48v DC: On-hook (ready to receive a call)
90v AC: Ring voltage
4-6v DC: Off-hook (customer wants to make a call or it is answering a ‘ring’ on the phone
What is the Integrated Service Digital Network? (ISDN)
- communication standards for simultaneous digital transmission of voice, video, data over traditional public switched telephone network
Explain the differences between the BRI and the PRI.
BRI (Basic Rate Interface)
- two 64 B-channels ,one 16 Dchannel.
- circuit can dedicate 128 Kbps toward voice/data transmission on a single copper cable pair.
- used for STE + VTC connections.
- B-Channels deliver data, D-channels used for signal management.
Primary Rate Interface (PRI)
- PRI = 23 64 B-channels one 64 D channel( totaling 24 channels. )
- PRI user can have up to 1, 544 Kbps.
- PRIs are primarily used for trunks between switches.
What happens to the analog signal when it is sampled and how does it turn digital when encoded with binary code using pulse code modulation?
- analog signal converted to digital signal.
- original signal transmitted by digital means.
Describe bandwidth.
maximum data that can be transmitted over a network connection in a given amount of time
How does sampling work in the Nyquist Principal, and when a higher rate is sampled, it can produce what?
- Sampling frequency greater x2 maximum frequency of signal being sampled
- produce perfect reconstruction of original signal
How are VTC audio and video signals compressed and decompressed?
in Realtime using a CODEC
Sound travels short distances but with the help of what device, it can travel further.
The telephone
What can affect the design of a telephone?
The frequency and amplitudes required
What controls the entire basic telephony network?
Call processing server/call manager.
Describe backbone cabling.
Backbone cabling = inter/intra-building cable connections in structured cabling between entrance facilities, equipment rooms and telecommunications closets
What are the mediums in which sound can travel?
Solid, liquid, and gas
What are the differences between land lines and dedicated lines?
- Land lines =connect many different locations
- Dedicated lines = connect 2 places continually (24 hours)
Define frequency.
- number of sound waves that pass a fixed point in a unit of time. (hertz hz)
Explain the differences between the PBX and the DID
A private branch exchange (PBX) is
- a small-scale telephone switch/software used to route calls for a building or organization.
Direct Inward Dialing (DID) is a service that provides a block of telephone numbers for calling into a company’s PBX system. (gets you directly to who you want to reach without going through an automated system.)
What is E911 used for?
Wireless E911 (Enhanced 911)
- displays telephone number + physical location of caller on operator’s screen.
Describe what PSAPS is and what the VOIP network being adopted.
Public Safety Answering Points (PSAPs) across the country need to be upgraded to digital/Internet Protocol (IP)-based 911 system.
-Next Generation 911 (NG911 is VOIP).(provides texts,video,etc slow implementation)
What is Class of Service?
- Each telephone line assigned Class of Service (CoS)
or - Calling Search Space (CSS) controls types of calls made from that line.
What is MLPP and describe its functions.
Multi-level Precedence and Preemption (MLPP)
- service allows authorized users to place priority calls, and if necessary, to preempt lower-priority calls.
Translate each section of a 10-digit U.S. phone number.
Three-digit numbering plan area (NPA) code
Three-digit Exchange code (NXX); the ‘exchange’ is the central office to which that number is assigned.
Four digits for the directory number (DN); assigned to the individual user.
Explain the differences between Customer Group and Device Pool.
- Customer Group = PSTN systems
- Device Pool= (VoIP) systems.
What are the benefits of the Caller ID service?
displays a caller’s phone number,location, and associated billing or subscriber name are shown.
The CID feature is particularly useful when screening known, unknown, or unwanted calls.
Explain both circuits switching and the automatic exchange switch.
Circuit Switching: connect telephone calls. used for the Public Switched Telephone Network (PSTN).
Automatic exchange switch: purpose eliminate human switchboard operator to complete the call.
The automatic switch used a series of selector based electrical switches in order to complete the circuit.
What does the call processing server do?
- center of VoIP phone system
- terminating all VoIP control connections.
What is packet switching?
chopping data into small packets, with address telling the network devices where to send them.
Define the DSN and how it functions in a crisis.
(Defense Switch Network)
The DSN assures connection availability w/ Multi-Level Precedence and Preemption (MLPP).
an emergency happens, phone line is needed, your call will be cut off so someone with higher priority can use the line.
_____ is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks.
VOIP (Voice over internet Porotocol)
All VoIP calls are dependent on what two qualities of the IP network?
Quality and Reliability
Describe the 5 major VoIP components
VoIP Protocols: A protocol= set of rules that defines how communications devices should communicate with each other and transmit data.
IP Network: provides infrastructure, backbone, necessary for a VoIP implementation.
Call Processing Server - stores end device IDs, directory numbers, configuration settings, and establishes calls. Program Installed on a Computer.
Endpoint devices - IP phones, soft phones, applications, computers, printers.
Voice Gateways: provide connectivity between VoIP components and PSTN components.
What does a codec do?
- device or computer program that encodes/decodes digital data stream
- signal or compresses and decompresses medial files.
Name and define each VoIP signaling protocol.
Signaling Protocols: used for VoIP components communicate w/ each other to prepare for the actual call.
Transport Protocols: After VoIP call is established, IP phones exchange voice packets with each other directly.
Proprietary: owned by specific entity
Non-Proprietary: free range (universal)
Name and define the VoIP transport protocol.
- needed for IP phones to exchange voice packets w/ each other.
-responsible for data formatting, identifying codec, sampling, carry actual voice traffic.
What is the difference between proprietary and non-proprietary?
Non-proprietary - anyone can use it.
Proprietrary - Only the company who owns it can use it.
Which of the named VOIP protocols are proprietary? Which are non-proprietary?
Proprietary :
- Skinny Client Control Protocol (SCCP or Skinny): SCCP is a Cisco proprietary VoIP signaling protocol.
non-proprietary :
- H.323, framwork defines components, functions, protocols to send voice/video over IP network
- Session Initiation protocol (SIP), establish/terminate mulitmedia sessions (layer 4) Voip signaling protocol most often used
- Real-Time Transport Protocol (RTP) responsible for managing the transmission of the voice data once call is established. Primary standard for transmitting audio over IP network.
In what scenario, would you utilize a voice gateway?
to access the IP network.
PSTN is analog phone whereas VoIP is __________ phone.
IP phone (TCP/IP phone or digital signaling).
QoS is implemented on which layer 3 network device?
Routers provide QOS.
Define QoS. What factors does QoS use to prioritize traffic?
- ability to give priority to certain types of network traffic.
- based on the application, user, or service that generated the traffic.
What does the router do for a packet?
forward packets from one subnet to another
What is the network switch used for?
- provide physical connectivity for devices to access an IP network.
provide two key services -
- Power Over Ethernet (POE)
- Voice Virtual Local Area Network (VLAN)
Define DSCP and what it uses in the header.
Differentiated Services Code Point (DSCP) - classifying/managing network traffic + providing (QoS) in layer 3 IP networks.
- uses 6-bit differentiated Service (DS) field in IP header for packet classification.
How can you group IP phone?
Subnet
What is the difference between VoSIP and SVoIP?
In a SVoIP implementation = connected to unsecure network. makes IP phone responsible for encrypting voice traffic.
Voice over Secure Internet Protocol (VoSIP)
- In a VoSIP implementation, connected to secure IP network.
