A glossary of business phone terms.

Terms are listed alphabetically. Four of them — interconnected VoIP, MLTS, dispatchable location and LNP — are United States regulatory categories rather than marketing words, and getting them wrong has consequences that a pricing mistake does not.

ACD (automatic call distributor)

Defined by the ATIS Telecom Glossary as "A device that distributes incoming calls to a specific group of terminals", which queues callers when everyone is busy: "If all terminals are busy, the incoming calls are held in a first-in-first-out queue until a terminal becomes available."1

The queue is the giveaway. An ACD is contact-centre equipment, built for a pool of interchangeable agents. Five tradespeople with different specialities are not a pool.

Auto attendant

The recorded menu that answers a business line and connects the caller according to the option they choose. Also called an automated attendant, virtual receptionist or phone tree; Google's documentation uses "automated attendant (auto attendant)".5

Unlike the other terms here it has no single standards-body definition — it is industry usage. The defining characteristic is that the caller makes the routing decision. See the full explainer.

DTMF (dual-tone multi-frequency)

The two-tones-per-key signalling that makes touch-tone dialling work, and therefore the input mechanism for every phone menu. Specified in ITU-T Recommendation Q.23, "Technical features of push-button telephone sets", published November 1988 and still formally in force.4

Its age is why a recorded menu works from any telephone on earth without an app.

Dispatchable location

A US regulatory term: under RAY BAUM'S Act, "the street address of the calling party, and additional information such as room number, floor number, or similar information necessary to adequately identify the location".7 The FCC's deadlines for providing it differ by device category — see emergency calling.

FOC (firm order commitment)

The confirmation a losing carrier returns against a port request, committing to a date. It follows the LSR. Industry process terminology rather than a defined regulatory term.

Hunting, and hunt group

ATIS defines hunting, in telephony, as "pertaining to the operation of a selector or other similar device to find and establish a connection with an idle circuit of a chosen group."2 A hunt group is that chosen group: a set of phones tried in order until a free one is found.

"Ring group" is the modern synonym — Google's documentation says "Ring groups, also called hunt groups".6

Interconnected VoIP service

A US regulatory category, defined at 47 CFR § 9.3 as a service that enables "real-time, two-way voice communications", requires a broadband connection and IP-compatible customer premises equipment, and "Permits users generally to receive calls that originate on the public switched telephone network and to terminate calls to the public switched telephone network."8

Falling inside it brings substantial 911 obligations. Classification is fact-specific; we make no claim about our own status, for the reasons set out on emergency calling.

LNP (local number portability)

The right to keep your number when changing providers. In the US the intervals are set by 47 CFR § 52.35: one business day for a simple wireline-to-wireline or simple intermodal port, four business days for a non-simple one.3 See porting your existing number.

LSR (local service request)

The order a gaining carrier submits to start a port. The rule attaches real consequences to its timing: "An accurate and complete Local Service Request (LSR) must be received by the current service provider between 8 a.m. and 1 p.m. local time", and anything later counts as received the next business day.3

MLTS (multi-line telephone system)

A US regulatory category defined at 47 CFR § 9.3 as "A system comprised of common control units, telephone sets, control hardware and software and adjunct systems, including network and premises based systems, such as Centrex and VoIP, as well as PBX, Hybrid, and Key Telephone Systems".8

It is broader than people expect, explicitly covering network-based and VoIP systems and non-profit and government deployments. Systems inside it carry Kari's Law and dispatchable-location obligations.

PBX (private branch exchange)

ATIS gives three definitions, including "A subscriber-owned telecommunications exchange that usually includes access to the public switched network" and "A private telephone switchboard that provides on-premises dial service".9

Historically a physical box; now usually software. The auto attendant was traditionally a feature inside one.

Port-out freeze

A lock some carriers apply to an account to prevent unauthorised transfers. It is an anti-fraud measure and only the account holder can lift it — and it is a common cause of a rejected port.

RespOrg (Responsible Organization)

For toll-free numbers, "The entity chosen by a toll free subscriber to manage and administer the appropriate records in the toll free Service Management System for the toll free subscriber."10 Moving a toll-free number means changing RespOrg, which is not an ordinary port. See local vs toll-free.

Ring group

A set of phones an option rings together, in sequence, or in rotation. The contemporary name for a hunt group, usually with more options than classic hunting. Designing your menu covers when to use each pattern.

Simple port

The class of port that gets the one-business-day interval. Notably, the term is not defined anywhere in the Code of Federal Regulations — it appears in the operative text of §§ 52.35 and 52.36 but in no definitional paragraph.

The nearest authoritative description is the FCC's consumer guidance: simple ports "generally do not involve more than one line or more complex adjustments to telephone switching equipment".11