Glossary for VoIP associated terms.

Acoustic Echo – Echo that is the result of feedback that is generated on any phone or speaker phone or headset from the speaker to the microphone.  (also see Line Echo)

ATA Analog Telephone adapter – A device that coverts analog voice signals to digital signals which can then be transmitted over the Internet.

Attendant (Auto Attendant) – An automatic response system, such as a voice presenting options such as press 2 for sales, 5 for Lisa, etc., which handles incoming calls and sends them to the appropriate phone or message.

Attenuation – (also referred to as loss) is a term that occurs with any type of signal, (digital or analog) and refers to the reduction in the strength of the signal, which is natural consequence of that signal traveling over the specific medium for long distances.

Backbone – A high speed fiber network with a large capacity that connects major cities throughout the world.

Bandwidth – Usually measured in 1000 bits per second (kbps), it is the amount of data that can be carried from one point to another in a given time period.

Baud – One signaling element per second, not to be confused with bits per second.

BOYD – Bring Your Own Device.  Some VoIP providers allow a person to supply their own equipment or ATA.

CDR – Call Record Detail.  Details about a specific call that includes duration, origination, destination, and billable information, as well as other pertinent information.

Cloud Communications – Cloud refers to the Internet.  Cloud Communications uses the Internet as a way to have users connect to host equipment at a remote location which then connect to other users allowing phone calls.  Synonymous with hosted VoIP or Internet Phone Service.

Codec – Normally used to reference to converting analog signals to digital or digital signals to analog.  It can be used in conjunction with compression software to compress and decompress these signals to varying degrees.

CPE – Customer Premises Equipment.  Equipment at the customers location that converts the digital signal back to voice.

CSU/DSU – Channel Service Unit/Data Service Unit.   A hardware device usually associated with a T1 that acts as an interface and converts data frames from a LAN to a WAN topology.

CSR – Customer Service Record.  A document required for all phone numbers that will show information that is tied to that number including services, billing activity, associated address and service orders.

Data – Usually treated as a synonym for information, but when used as a description for network topology refers to all traffic other than voice.

Data Transfer Rate – The speed of travel of a given amount of data from one place to another.

DHCP – Dynamic Host Control Protocol.  A communications protocol that lets network administrators supervise and distribute IP addresses from a central point to each computer or device on a network.

DID – Direct Inward Dialing.  A service that allows an enterprise to allocate individual phone numbers to each person within its PBX system.

DSL – Digital Subscriber Line.  Phone technology that allows a broadband internet digital connection to be carried over existing copper phone lines, while still allowing the phone service carry analog signals over the same line.

DTMF – Dual Tone Multi-frequency.  Also known as Touchtone, it is the signal generated when you press a telephone’s touch keys that is sent to the telephone company.  These signals are actually two tones of a specific frequency designed so that a voice cannot duplicate them.  The ability for interactive telephone menus to work correctly across different networks and phone systems is due to the fact that DTMF tones are standardized and are uniquely linked to a number (and # or *) on the telephone keypad.

Echo Cancellation – Echo cancellation is the process of eliminating echo from voice communication to improve the quality of the call. It is necessary because speech compression techniques and packet processing delays generate echo, of which there are 2 types, acoustic echo and hybrid echo. Echo cancellation improves voice quality in VoIP calls and also reduces the required bandwidth due to silence suppression techniques.

ECM – Error Correction Mode.   Used in conjunction with memory storing fax machines, ECM allows for the receiving fax machine to request retransmission for a page where some errors were detected in the frames of that page.  If the receiving fax machine is unable to receive an error free page the fax transmission may fail and the fax connection terminated.  On networks with some packet loss, fax transmissions will routinely fail when ECM is enabled because of the low tolerance allowed for any packet loss.

GR-909 Test – A standards based suite of electrical tests that have been adapted for the VoIP industry and test for such problems as unwanted voltage on the phone lines, an off hook device keeping the line open, and even when no phone is connected on the line.  Some VoIP routers include the GR-909 test in their diagnostic tools.

IAD – Integrated Access Device.  Equipment at the customers location that is used to convert digital signals back to voice.  Usually used in association with a DSL connection.

IAX – Inter-Asterisk eXchange Protocol, (pronounced “eeks”) (now commonly meaning IAX2) is an Asterisk communications protocol for setting up interactive user sessions (both audio and/or video) and supports any type of codec.

IVR – Interactive Voice Response.  An integrated software information system that speaks to callers and uses menus and voice responses.  By using touch-tone keypad entries to interact with the software, you get voice responses with real time data.

Jitter – As data load increases and decreases, routers on the Internet can create slightly different times that individual packets take to travel from one point to another point.  This variation in time is known as jitter.

Latency The time it takes for a packet to reach its destination.  Higher delay times can be an issue, especially for VoIP, where voice delay can be recognized with latency higher than 150 milliseconds.  Higher than 500 milliseconds and the conversation is going to be very problematic.

LERG – Local Exchange Routing Guide.  Is a database of the first 6 digits of a telephone number, updated on a regular basis, that provides information for routing telephone calls over the Public Switching Telephone Network, as well as, enables identification of what local company the number belongs to.

Line Echo – Echo that is common in the PSTN network and is created as a result of voice traveling over hybrids or 2 wire to 4 wire conversions.

LNP – Local Number Portability is the ability of a US telephone customer to retain their phone number if they switch to another local telephone provider.

MOS – Mean Opinion Score.  The Mean Opinion Score (MOS) provides a numerical indication of the perceived quality of voice transmission after compression and/or transmission and is expressed as a number in the range 1 to 5, where 1 is lowest perceived audio quality and 5 is the highest perceived audio quality measurement.

MTA – Multimedia Terminal Adapter.  A device that connects a traditional telephone to a cable line, converting analog voice to digital signals.

NAT – Network Address Translation.  An Internet standard allowing a local network to use one public IP address to connect to the Internet and a set of local IP addresses to identify each PC or device in the local network.  NAT translations are a challenge for VoIP and result in one-way audio in some cases.

PBX – Public Branch Exchange.  A private telephone switching system that allows outside phone lines from a telecommunications provider to connect to extensions within the office or building.  They usually have multiple features including call forwarding, rollover, paging and voice mail.

POTS – Plain Old Telephone System.  The familiar single phone line, single phone number system that has been in existence for many years.

PRI – Primary Rate Interface.  The Primary Rate Interface consists of 23 B-channels and one 64 Kpbs D-channel using a T-1 line and can have up to 1.544 Mbps service.   Typically, it is a dynamic circuit that delivers both voice and data, giving preference for voice.  When a channel is not carrying voice it is automatically allocated for data.

PSTN – Public Switched Telephone Service.  The combination of local, long-distance and international carriers that make up the worldwide telephone network.

Rate Center  – The geographic area used by local exchange carriers to set rate boundaries for issuing phone numbers and for billing.  Rate centers are important when considering porting of numbers through LNP to and from VoIP service providers.

RJ-11 –  The typical four or 6 wire connector used to connect telephone equipment.

RJ-45 – An 8 wire connector used to connect Ethernet connections in computers, routers and other Internet devices.  This connector is slightly larger than a (RJ-11) telephone connector.

Router – A router is a device connected to at least two networks that determines the next network point to forward a packet to.  The decision of which way to send each information packet is based on it’s current understanding of the networks that it is connected to.

RTP – Real Time Transport Protocol.  An Internet protocol that functions for end-to-end network connections for applications that use audio or video.+

Satellite Phone – A satellite phone is a particular type of mobile phone that connects to earth orbiting satellites instead of the typical terrestrial cell towers that most cell phones connect to. The features on most systems are similar to traditional mobile telephones and transmit voice, short messaging service and allow low-bandwidth internet access are supported. Depending on the particular system the coverage may include the entire Earth, or only specific regional areas.

Silence Suppression and Comfort Noise Generation – Silence Suppression is a means of increasing the number of calls supported by reducing the bandwidth for a single call.  If speech is not present, the silence suppression and comfort noise generation is activated. This is accomplished by removing and not transmitting the natural silence that occurs in normal two-way connection. Comfort Noise Generation provides an artificially-generated background white noise to reassure callers that their calls are still connected during silent periods rather than thinking the call dropped.

SIP – Session Initiation Protocol is a signaling protocol for Internet conferencing, telephony, and instant messaging.  It is a request-response protocol, dealing with requests from clients and responses from servers. initiating an interactive user session.

SIP – Session Initiation Protocol Trunking is the use of VoIP to facilitate the connection of typically a PBX to the Internet, where the Internet replaces the conventional telephone trunk, allowing a business to communicate with traditional PSTN telephone subscribers worldwide by connecting to an ITSP (Internet Telephony Service Provider).  SIP trunking can save money and offer services to an IP-PBX.

Soft Phone –  IP telephony software that allows end users to send and receive calls over the computer or hand held PC device (PDA) over the Internet.  Typically used in conjunction with a headset and microphone there are many free softphones that are available.

STUN – Simple transversal of UDP through NATs  is a protocol for assisting devices behind a NAT firewall or router with their packet routing.

Switch  – A switch is a device that keeps a record of the MAC addresses of all devices connected to it and then channels incoming data from any of multiple input ports to the specific output port that will take the data toward its intended destination.

T38 – A recognized standard for sending fax transmissions over an IP network in real time mode. Messages are sent as UDP or TCP/IP packets.

UDP – User Datagram Protocol is a communications protocol that does not provide sequencing of the packets. The application must be able to make sure that the entire message has arrived and is in the right order.

VAD – Voice Activation Detection is a software application, also known as silence suppression that allows the detection of the absence of audio for a specified amount of time to use techniques to conserve bandwidth, as many conversations can actually include one half silence. Voice activation detection can also be used to forward idle noise or comfort noise to a remote IP telephone or IAD giving the illusion of a constant transmission stream during silence, so the listener would not think the line had gone dead.

VoIP – Voice over Internet Protocol.  The transmission of voice over the Internet as digital packets rather than the traditional circuit-committed protocols of the PSTN.  VoIP uses real-time protocol (RTP) to help ensure that the packets get delivered in a timely way.  For a full explanation about the benefits and features of Voice over IP read what is VoIP.