Asterisk PBX Terminology

Asterisk® PBX Glossary of Terms

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Acoustic Echo Echo resulting from the feedback that is generated on any phone or speaker phone or headset from the speaker to the microphone.
ATA (Analog Telephone Adapter) A device that coverts analog voice signals to digital signals which can then be transmitted over the Internet. These devices, some having two FXS ports, which are standard telephone ports where a traditional telephone can plug in, and an RJ45 port for connection to the Internet, can be used to connect analog devices, as extensions to a VoIP system. A popular model is the Cisco SPA112. To view a picture of the SPA112 showing the ports and get the very best price.
Attendant (Auto Attendant) An automatic response system, such as a voice presenting options, such as press 3 for sales, 4 for parts, 5 for John, etc. An attendant can handle incoming calls and direct them to the proper person, department or extension. (Attendants are different than IVRs in that Attendants direct callers to make a choice and then push that number on the phone, where IVRs (Interactive Voice Response) can use a voice response to direct the call.
Asterisk® An Open Source business phone system or PBX system operating software. Owned by Sangoma, it is recognized as the gold standard by the open source development community and has proved stable, reliable and robust with the ability to accomplish and integrate with numerous feature sets. Used globally, Asterisk has demonstrated its capacity to power phone systems for the the very small company all the way to enterprise level corporations.
Asterisk® Appliance Another reference to a phone system that uses Asterisk as its software to handle the features and call routing. These devices can be a computer or other hardware device and are also known as the business phone system box.
Baud One signaling element per second, not to be confused with bts or bits per second.
Bufferbloat Excessive latency when a router or switch is configured to use inordinately large buffers, causing packets to become queued for long periods in these oversized buffers. In a first-in first-out queuing system, data sits for longer periods causing higher latency degrading the network, especially for VoIP and gaming.
Busy Lamp Field A set of lights or LEDs, found primarily on an attendant console that visually indicates which phones on the system are in use.
Carrier A telecom company that provides telecommunications circuits. They can include local telephone companies and other telecom companies such as cable providers and SIP or VoIP providers.
Cloud Communications Cloud, which refers to the Internet, Communications uses the Internet as a way to have users connect to host communications equipment such as a PBX at a remote location which then connect to other users allowing phone calls. Synonymous with hosted VoIP or Internet Phone Service.

Codec A term that comes from the enCOder/DECoder or Compressor-Decompressor process used for software or hardware devices that can convert a data stream. Two VoIP codecs often used are G711, a non-compressed codec, and G729, a codec that uses compression to lower bandwidth requirements.
Convergence Referred to in the telecom and IT world as the integration or connection of different systems. Convergence will allow for communication and "meeting" of separate systems to allow for better efficiencies. An example would be the phone systems voicemail integrating with Outlook. Asterisk systems allow for voicemails to be received as an attachment in an email which can be listened to. Deleting the email with attachment in Outlook if fully "converged" would also delete the voicemail off of the Asterisk server.
CPE (Customer Premise Equipment) Equipment that resides on premise, usually at or with a business or customer.
CTI (Computer Telephony Integration) Is the use of computers to manage telephone calls, allowing for automation possibilities which allows for integration of text and faxing and other services.

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.
DID (Direct Inward Dialing) A service that allows a company to allocate individual phone numbers to each person within its PBX business phone system. Calling that individual number will bypass other call treatments and go directly to the individual's phone.
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 to carry analog signals over the same line.
Dynamic Jitter Buffer As a ATA receives voice packets they are stored briefly, rearranged and then processed in predefined intervals to reduce distortion.
Echo Cancellation Echo cancellation uses both hardware and software as a process of eliminating echo from voice communication, improving the quality of the call. Generally necessary because speech compression techniques and packet processing delays generate echo. Two types of echo exist, 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 with memory storing in fax machines, ECM allows the receiving fax machine to request retransmission for a transmitted 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 that have some packet loss, fax transmissions will typically fail when ECM is enabled because of the low tolerance allowed for any packet loss.
FXO (Foreign eXchange Office) FXO designates a telephone signaling interface that receives POTS, or "plain old telephone service". It generates the off-hook and on-hook indications (loop closure/non-closure). These interfaces are ports or connections on the phone system.
FXS (Foreign eXchange Station) is the interface (port) on a business phone VoIP device for connecting directly to phones, faxes and some other devices.
Gateway A hardware device that converts traditional PSTN (analog/T1) signals into IP, bridging the two protocols and allowing them to communicate with each other. Some gateways can be FXO or FXS connections to Ethernet.

IAX (Inter-Asterisk eXchange protocol) An Asterisk PBX protocol, (Now most commonly refers to IAX2), that usually carries both signaling and data on the same path and is used to enable VoIP connections between servers as well as client-server communication. SIP protocol has become the standard in signaling protocols, especially after VoIP has become so dominant even though in some cases IAX is still being used.
IP Phone A phone that connects using Internet Protocol instead of more traditional analog lines. An IP phone is more computer like, allowing advanced feature sets and other software functionality. Typically these phones have two Ethernet ports, one for the connection back to the Asterisk phone PBX device and the other to the user's PC. The phone acts a switch allowing both to connect to the network through one wall connection.
IVR (Integrated Voice Response) An integrated software information system that speaks to callers and uses voice responses. The voice response will direct the system to route the call or choose the next response in the IVR tree. By using touchtone keypad entries to interact with the software, you get voice responses with real time data.
JITTER The variation, (usually measured in milliseconds), between packets arriving at their destination, which is caused by queuing, contention and other effects on their travel through the network.
LAN (Local Area Network) A network located in the same premise or small geographic area that is used to connect computers and other devices together through cabling or wireless connections enabling data to be sent from one point to another.
Latency The time (usually measured in milliseconds) it takes data or voice packets to travel from one point on a network to another point.
Line Echo Echo that is common in the Public Switched Telephone network and is created as a result of voice traveling over hybrids or 2 wire to 4 wire conversions.
LNP (Local Number Portability) The ability of a US telephone customer to retain (or "port") their phone number if they switch to another local telephone provider.
MPLS (Multi-Protocol Label Switching) An IETF initiative that integrates layer 2 information about network links (latency, bandwidth, utilization) into layer 3 or IP within a autonomous network, which greatly improves IP-packet exchange. These advancements give network operators the ability and flexibility to re-route traffic around failure points, congestion and bottlenecks for a more robust stable network for their network users.

Packet Loss During a transmission some of the data that is sent in packets are lost due to latency, congestion at a router or other network problems. Packet Loss is specifically problematic to VoIP and even a small amount can result in significant voice degradation in the quality of the voice.
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. T hey usually have multiple features including call forwarding, rollover, paging and voicemail. PBX phone systems have become synonymous with "a business phone" system.
POTS (Plain Old telephone System) The familiar single phone line, single phone number system that has been in existence for many years, typically a copper line.
PPPoE (Point to Point Protocol over Ethernet) PPPoE is a dedicated connection type that is most often used for DSL connections. Connections authenticate using a username and password.
PRI (Primary Rate Interface) Each T1 circuit contains 24 separate channels. A PRI reserves one channel to carry special signaling and other information such as Caller ID, etc. for the other remaining channels. PRIs allow for multiple DIDs to be directed to individual phones once they reach the phone system.
PSTN (Public Switched Telephone Network) The traditional telephone network which uses pairs of copper wire to carry analog signals or digital T1 signals carrying multiple channels.
QoS (Quality of Service) QoS refers to a network system's ability to sustain a given service at or above its required minimum performance level. With VoIP this pertains to prioritizing voice data, usually RTP packets, over other services like Internet surfing, email, etc.
RJ-11 The typical 4 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.

SIP (Session Initiation Protocol) 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 Trunking Using SIP (Session Initiation Protocol) to connect with an ITSP (Internet Telephony Service Provider) from a PBX or Asterisk phone system for primarily voice communications, which can benefit the end user with lower cost calls. For companies to take full advantage of their premise phone systems, which communicate over IP within the enterprise, they can have one or more SIP trunks configured to connect to a traditional PSTN network though an Internet SIP connection. The benefits can include lower monthly calling costs for long distance as well as International calling.
Soft Phone IP telephony software that allows end users to send and receive calls over their computer or a hand held PC device (PDA) over the Internet. Typically used in conjunction with a headset and microphone.
T1 A digital transmission link with a capacity of 1.544 Mbps using two pairs of normal twisted wires. T1s usually have 24 voice channels, each one of 64 Kbps.
T38 A recognized standard for sending fax transmissions over an IP network in real time mode. Faxing over VoIP can be a significant challenge and T38 sets standards that facilitate faxing over IP.
Trunk Line When dealing with a business phone system, trunk lines are the phone lines coming into the phone system from the telephone provider, verses extensions which typically connect to desk phones. Trunk lines are often referred to as phone lines. These lines can connect into FXO ports on a phone system.
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 the packets get delivered in a timely way.
VPN (Virtual Private Network) Using tunneling, IP traffic is securely encrypted between two endpoints so that the transmission travels securely over a public TCP/IP network.
WAN (Wide Area Network) A geographically disperse network that encompasses routers and other devices over a large area and can route that data to the proper endpoint.
WebRTC (Real Time Communications over the Web) WebRTC is an open source project based on HTML5 and JavaScript with the objective of using the web to advance communications. It is designed to use the browser and mobile platforms to communicate using a common set of protocols without having to install additional plugins or software. WebRTC essentially offers an open framework including the building blocks that enables secure Real Time Communications, such as audio and video.