The Business Phone Glossary: 50 Telecom Terms Explained in Plain English

Phone system quotes are written in a dialect that assumes the reader already speaks it. Line items refer to DIDs, channels, trunks and SBCs; support tickets mention jitter and MOS; the salesperson says hosted when they mean cloud and PBX when they mean phone system.

This is the translation. Terms are grouped by where you will meet them, and the ones that genuinely affect a buying decision are flagged as such.

The Basics

PBX — Private Branch Exchange. The phone system itself: the thing that decides which phone rings, handles transfers and holds voicemail. Originally a physical box on your wall; now usually software.

Cloud PBX / Hosted PBX — the same phone system, run in a provider’s data centre and delivered over the internet. No box on your wall. The two terms mean the same thing in practice. Matters when buying.

On-premise — a PBX physically in your building, owned and maintained by you.

Hybrid — a local PBX for internal calls plus cloud services for everything else. Common where a business has recently invested in hardware.

VoIP — Voice over Internet Protocol. Carrying calls over data networks instead of dedicated copper. The underlying technology in essentially all modern systems.

UCaaS — Unified Communications as a Service. Voice, video, messaging and presence sold together as one subscription.

CPaaS — Communications Platform as a Service. Calling and messaging exposed as an API for your own software to use.

PSTN — the Public Switched Telephone Network. The traditional worldwide phone network. “PSTN replacement” means moving off it.

POTS — Plain Old Telephone Service. A single analogue line. The term is not a joke; it is the industry’s own.

Numbers and Lines

DID / DDI — Direct Inward Dial. A phone number that reaches a specific person or department without going through a switchboard. When a quote lists DIDs, it means numbers. Matters when buying.

876 — Jamaica’s area code. An 876 number signals a local business to anyone dialling it.

Toll-free — a number the caller does not pay for, because you do. 1-888, 1-877 and similar.

Vanity number — a number chosen so the digits spell something memorable.

Porting — moving an existing number from one provider to another so you keep it. Matters when buying — it has a timeline and paperwork requirements.

Caller ID / CLI — the number shown to the person you are calling. Configurable, and worth configuring; customers ignore numbers they do not recognise.

Number masking — presenting the business number instead of a staff member’s personal one.

SIP trunk — the voice path connecting a phone system to the public network over the internet. Replaces physical lines. Matters when buying.

Channel / concurrent call — one simultaneous conversation. Ten channels means ten calls at once, regardless of how many phones you own. Matters when buying — this is what you are actually sizing.

PRI / T1 / E1 — older digital line technologies that carry multiple channels over one circuit. Being retired, but still in service at sites with legacy PBXs.

Analogue line / FXS / FXO — the traditional two-wire connection. FXS is the port a handset plugs into; FXO is the port that connects to a phone line.

Voice gateway — hardware that converts between analogue or digital lines and VoIP, letting old handsets work on a modern network.

Call Handling

Auto-attendant / IVR — the recorded menu that answers and offers options. IVR strictly means Interactive Voice Response, which includes menus that read out information or collect account numbers.

Extension — the short internal number for a person or device.

Ring group — several phones ringing together, or in sequence, for one incoming call.

Hunt group — a ring group that tries extensions in a defined order rather than all at once.

Call queue — callers wait in line, with hold music, for the next free agent. Distinct from a ring group: a queue holds people, a group just rings.

ACD — Automatic Call Distribution. The engine that decides which queued caller goes to which agent.

Skills-based routing — sending callers to agents qualified for their specific issue.

Blind / cold transfer — passing a call on without speaking to the recipient first.

Warm / attended transfer — speaking to the recipient before passing the call.

Call park — putting a call in a numbered holding slot so any phone can retrieve it.

Find me / follow me — a call chasing you across desk phone, mobile and app.

Day / night mode — different call flows inside and outside business hours.

Failover — where calls go when the primary path fails. Matters when buying.

Overflow — where calls go when every agent is busy.

Callback / virtual queue — the caller hangs up but keeps their place, and the system rings them back.

Whisper — a supervisor speaking to an agent, unheard by the customer.

Barge — a supervisor joining a live call audibly.

Quality and Network

Jitter — variation in packet arrival timing. Heard as choppy or robotic audio.

Latency — one-way delay. Above roughly 150ms, people start talking over each other.

Packet loss — data that never arrives. Heard as dropouts and missing syllables.

MOS — Mean Opinion Score. Call quality rated 1 to 5; above 4 is good.

QoS — Quality of Service. Router configuration that gives voice traffic priority over everything else. Matters when buying — the single highest-value network change for call quality.

Codec — the compression scheme for audio. G.711 uses more bandwidth and sounds better; G.729 uses less and sounds slightly worse.

PoE — Power over Ethernet. Phones powered through the network cable. Useful for tidiness and, on a UPS, for resilience.

SBC — Session Border Controller. Security and interworking equipment sitting between your network and the provider’s.

NAT — the router function that shares one public address among many devices. Historically the cause of a great deal of one-way audio.

Dual WAN — two internet connections with automatic failover between them.

Measurement and Contracts

ASA — Average Speed of Answer. How long callers wait before a human picks up.

AHT — Average Handle Time. Talk time plus after-call work.

ACW — After-Call Work. Admin an agent does after hanging up, during which they cannot take another call.

FCR — First Call Resolution. The share of issues settled without a second call. The metric most tied to customer satisfaction.

Abandonment rate — callers who hang up before being answered.

CDR — Call Detail Record. The log entry for a call: who, when, how long, what happened.

SLA — Service Level Agreement. What the provider commits to, and what happens when they miss it. Matters when buying — read the remedies, not just the percentage.

Uptime % — 99.9% permits nearly nine hours of downtime a year; 99.999% permits about five minutes. The gap between those two figures is enormous.

Toll fraud — criminals using your phone system to make expensive calls at your cost.

The Ten That Actually Decide a Purchase

If you read no further: channels (how many simultaneous calls you are buying), DIDs (how many numbers), porting (whether you keep yours and how long it takes), QoS (whether your network is ready), failover (what happens when something breaks), SLA (what the provider owes you), caller ID (what customers see), hosted vs on-premise (who maintains it), PoE (how phones are powered), and toll fraud protection (who pays if it happens).

Everything else in this list is useful vocabulary. Those ten are where money and risk actually sit.

For a plain-English walk through your own quote — ours or anyone else’s — call WOCOM on 876-326-1212 or message us on WhatsApp. The ultimate guide to business phone systems in Jamaica covers the buying process end to end.