Appendix A. Commonly Used VoIP Terms

This Appendix covers some acronyms and terms used throughout the book, which are also common terms in Telephony. The Appendix can be used as a quick reference to the terms when reading the book or while configuring the TrixBox system.

ACD: Automatic Call Distributor is a feature used to route calls in a call center environment to the appropriate person based on factors such as availability, call usage, time, etc.

Agent: Member of a queue.

AGI: Asterisk Gateway Interface.

ATA: Analog Telephone Adapter, a device used to connect an analog phone to a digital line.

BRI: Basic Rate Interface. This is an ISDN communications standard for voice capabilities.

CDR: Call Detail Record. This is the log of a call.

Codec: A Codec is a piece of code that encodes or decodes audio using a given type of algorithm.

CRM: Customer Relationship Management.

DID: Direct Inward Dialing simply refers to the phone number dialled by a caller to reach our telephone system.

DISA: Direct Inward System Access.

Firewall: A device that exists at the border of two or more networks or network segments, and applies policies to the traffic that traverses those borders based on the security requirements of the network.

Follow-Me: This feature of TrixBox uses ring groups to allow a user to float between multiple extensions.

FXO: The Foreign eXchange Office is the end point of a connection. It is the FXO device that receives a call.

FXS: A Foreign eXchange Station is the sender of the call to an end-point device.

IAX: Inter-Asterisk eXchange protocol. The protocol is developed by Digium as a simpler and easier‑to‑manage alternative to using SIP for VoIP.

ISDN: Integrated Services Digital Network. This gained some popularity within small to medium-sized businesses as a cost-effective way of connecting to the PSTN and getting some advanced services, like many lines to one office or voice and data lines on one service. ISDN is a digital service and offers a few more features over POTS.

ITSP: An Internet Telephone Service Provider can deliver telephone network connectivity to our Asterisk PBX over Internet rather than over analog phone lines that need to be physically installed at our location.

IVR: Interactive Voice Response is known in the TrixBox system as the Digital Receptionist. This is the system that creates voice-prompt menus to help callers locate the appropriate person to speak to.

Hard phone: This is a hardware-based telephone.

NAT: Network Address Translation protocol.

Overhead Paging: Public Announcement System.

PBX: PBX (Private Branch eXchange) refers to the telephone switching system installed in a private location such as our office.

POTS: Plain Old Telephone Service. This is commonly used for residential purposes. POTS is an analog system and is controlled by electrical loops. It is provided by copper wires run to residences and places of business and is therefore the cheapest and easiest telephone service to roll out.

Predictive Dialer: Predictive Dialer is a software that dials ahead of a user in order to determine if the dialled number is answered by a human rather than by a fax machine or is ringing out. It is used in call centers to increase productivity.

PRI: Primary Rate Interface. This is an ISDN communications standard for voice capabilities (See also BRI).

PSTN: Public Switched Telephone Network refers to the public phone network that carries all traditional phone calls.

Queues: A call queue is a function that places callers into a waiting room while they wait for the next available agent.

Ring Groups: A ring group is a collection of extensions that will all ring at the same time when a call is transferred to the group's extension number.

SIP: Session Initiation Protocol. This is a commonly used VoIP protocol.

SoftPhone: This is a software-based telephone.

Trunk: A trunk is a channel that operates between two distinct points. This can be either between PBXs within an organization, or between the organization's PBX and its provider.

T1/E1: This is common in larger companies, although in recent years it has become more affordable. T1/E1 is a digital service and offers yet more features than ISDN, the most important feature being increased bandwidth that translates, in telephony, to more telephone lines.

VoIP: The term VoIP simply means the ability to send voice communication over existing network wires using the same methods that are used for other internet services such as email, web surfing, or instant messaging.