Telephony has been accumulating jargon since the 1870s, and vendors wield it freely. This page defines the terms that actually come up when businesses buy, run, or troubleshoot phone systems, one or two honest sentences each. Terms with a full guide link to it.
A2P
Application-to-person messaging: texts sent through software on behalf of a business. Registered and routed differently from personal texting. Full guide.
ATA
Analog telephone adapter: the box that lets fax machines, cordless phones, and door buzzers work on a VoIP system. Full guide.
Attestation
The confidence level (A, B, or C) a carrier attaches to a call's caller ID under STIR/SHAKEN. Weak attestation invites 'Spam Likely' labels. Full guide.
Auto attendant
The menu that answers and routes callers: 'press 1 for sales.' Simpler than an IVR, which also interacts with data. Full guide.
BYOD
Bring your own device: using phones you already own with a new provider. Most standard SIP desk phones qualify.
Call queue
A waiting line for callers, with hold position, callbacks, and rules for distributing calls to available staff. Full guide.
CNAM
The database system carriers query to display a caller's name. The name does not travel with the call; it is looked up. Full guide.
Codec
The algorithm that turns voice into data: G.711 (landline quality), G.722 (HD), Opus (modern, adaptive). Full guide.
DID
Direct inward dial: a full public phone number pointed at a specific person or function, bypassing the main menu. Full guide.
Dispatchable location
The address plus floor/suite detail that must accompany a 911 call under RAY BAUM'S Act. Full guide.
DND
Do not disturb: a per-extension status that sends calls straight to the next rule (usually voicemail).
E911
Enhanced 911: emergency calling that carries the caller's registered location to dispatchers. Full guide.
Extension
An internal destination on a phone system: a person, desk, or function. Distinct from a phone number. Full guide.
Failover
Pre-configured rules for where calls go when a device, office, or network is unreachable. Full guide.
Find-me/follow-me
Sequenced ringing rules: try the desk, then desk plus cell, then voicemail, varying by schedule. Full guide.
Hosted PBX
A phone system running in a provider's data center instead of a box in your closet. Also called cloud PBX. Full guide.
Hunt group
A group that rings members one at a time in a defined order until someone answers. Full guide.
IVR
Interactive voice response: a menu system that also interacts with data ('enter your account number'). Full guide.
Jitter
Variation in packet arrival timing. Above roughly 30 ms, audio turns choppy. Full guide.
Latency
The time a voice packet takes to arrive. One-way latency under about 150 ms feels natural. Full guide.
MMS
Multimedia messaging: texts carrying images or media, delivered by a different mechanism than SMS. Full guide.
MOS
Mean opinion score: the 1-to-5 call quality scale; 4.0+ is business grade. Full guide.
NAT
Network address translation: how routers share one public IP among private devices. The root of most one-way-audio problems. Full guide.
PBX
Private branch exchange: the system that routes a business's calls among its extensions. Full guide.
PoE
Power over Ethernet: electricity delivered through the network cable, powering desk phones without adapters. Full guide.
Porting
Moving a phone number between providers. A federally protected right; your number is yours. Full guide.
POTS
Plain old telephone service: traditional analog copper lines, now being retired. Full guide.
PSTN
Public switched telephone network: the global traditional phone network VoIP interconnects with. Full guide.
QoS
Quality of service: router settings that prioritize voice packets ahead of bulk traffic. Full guide.
RespOrg
Responsible organization: the entity managing a toll-free number's registry entry. Full guide.
Ring group
A group whose phones all ring simultaneously; first to answer takes the call. Full guide.
RTP
Real-time transport protocol: the stream that carries the actual call audio, separately from signaling. Full guide.
SBC
Session border controller: carrier equipment that secures and manages VoIP traffic at network boundaries.
SIP
Session initiation protocol: the signaling language that sets up, connects, and ends VoIP calls. Full guide.
SIP ALG
A router 'helper' feature that rewrites VoIP traffic, and breaks it so often that disabling it is standard practice. Full guide.
SIP trunk
Virtual phone lines delivered over the internet, typically feeding an on-premise PBX. Full guide.
SMS
Short message service: the original 160-character text message, split into 153-character segments when longer. Full guide.
Softphone
A phone that exists as software: an app carrying your business extension on a computer or smartphone. Full guide.
SRTP
Secure RTP: encryption for the audio stream itself, preventing eavesdropping in transit. Full guide.
STIR/SHAKEN
The caller ID authentication framework US carriers use to fight spoofing. Full guide.
T.38
The fax relay protocol that makes faxing reliable over IP networks. Full guide.
TCPA
The federal law governing automated calls and texts to consumers, with statutory damages per violation. Full guide.
Toll fraud
Attackers using stolen calling access to pump calls to premium numbers, the dominant VoIP crime. Full guide.
UCaaS
Unified communications as a service: calling, messaging, and meetings bundled as one cloud subscription. Full guide.
Vanity number
A number chosen for the word its digits spell, like 1-800-FLOWERS. Full guide.
VoIP
Voice over Internet Protocol: phone calls carried as data over the internet. Full guide.
Wideband / HD voice
Codecs capturing roughly double the audio range of a landline, making calls sound noticeably fuller. Full guide.
10DLC
The registration framework for business texting from regular 10-digit numbers. Full guide.
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