Glossary

VoIP & Cloud Phone Glossary

60+ business communication terms defined in plain English.

VoIP: Voice over Internet Protocol — technology that carries voice calls over an IP network instead of the traditional PSTN.
SIP: Session Initiation Protocol — the signaling standard used to set up, manage, and tear down VoIP calls.
PBX: Private Branch Exchange — a business phone system that routes calls internally and to external lines.
Cloud PBX: A PBX hosted by a provider in the cloud, eliminating on-premise hardware and maintenance.
UCaaS: Unified Communications as a Service — voice, video, messaging, and collaboration delivered as a cloud service.
CCaaS: Contact Center as a Service — a cloud-delivered platform for inbound and outbound customer engagement.
DID: Direct Inward Dialing — a virtual phone number that routes external calls directly to a user or team.
IVR: Interactive Voice Response — automated menu that lets callers navigate options using voice or keypad.
ACD: Automatic Call Distribution — routes inbound calls to the best-available agent based on rules.
SBC: Session Border Controller — a device or service that secures and controls VoIP traffic at network boundaries.
Number Porting: The process of transferring an existing phone number from one provider to another.
Toll-Free Number: A phone number where the receiver pays for the call, often used for customer service lines.
Local Presence: Displaying a caller ID number local to the recipient's area to increase answer rates.
Softphone: A software application that lets users make and receive calls from a computer or mobile device.
Codec: An algorithm that compresses and decompresses voice data for efficient transmission.
Jitter: Variation in the time it takes voice packets to arrive, which can degrade call quality.
Latency: The delay between when a voice packet is sent and when it is received.
MOS: Mean Opinion Score — a 1-to-5 measure of perceived call quality.
QoS: Quality of Service — network settings that prioritize voice traffic for consistent call quality.
SLA: Service Level Agreement — a contractual guarantee of uptime, quality, or support response.
E911: Enhanced 911 — emergency calling that transmits the caller's location to first responders.
10DLC: 10-digit long code messaging — the US carrier framework for compliant business SMS.
A2P: Application-to-Person messaging — SMS sent from a business application to consumers.
Omnichannel: A customer engagement approach that unifies voice, chat, email, SMS, and social in one experience.
CTI: Computer Telephony Integration — connects phone systems to business applications like CRM.
Call Whisper: A message played to the agent (not the caller) before a call connects, often revealing context.
Call Barge: A supervisor joining an active call to speak with both parties, usually for training.
Call Monitor: A supervisor listening silently to an active call.
Voicemail Transcription: Automated conversion of voicemail audio into text.
Presence: Real-time indicator of a user's availability (available, busy, on a call).
AHT: Average Handle Time — mean duration of a customer interaction, including talk and after-call work.
FCR: First Call Resolution — the percentage of customer issues resolved on the first contact.
CSAT: Customer Satisfaction Score — a post-interaction rating of the customer experience.
NPS: Net Promoter Score — likelihood a customer would recommend a brand, scored -100 to +100.
SIP Trunk: A virtual line that connects a PBX to the PSTN over the internet.
BYOC: Bring Your Own Carrier — using your existing carrier with a new UCaaS platform.
Softswitch: Software that connects voice calls between endpoints, replacing legacy hardware switches.
PSTN: Public Switched Telephone Network — the legacy circuit-switched phone network.
Elastic SIP: Programmable SIP trunking that scales capacity automatically with demand.
Failover: Automatic redirection of calls to a backup route when the primary path fails.
Geo-Redundancy: Duplicate systems in multiple geographic regions to survive regional outages.
HD Voice: Wideband audio (7 kHz+) that delivers clearer, more natural voice quality.
Call Flip: Moving an active call between devices — desk phone to mobile, mobile to laptop — without dropping.
Screen Pop: A CRM screen that automatically opens when a call connects, showing caller context.
Predictive Dialer: An outbound dialer that connects agents only to answered calls, using pacing algorithms.
Power Dialer: An outbound dialer that dials one number at a time per available agent.
Progressive Dialer: An outbound dialer that dials the next number after an agent completes a call.
Wrap-Up Time: Time an agent spends on after-call work before taking the next contact.
Skills-Based Routing: ACD strategy that sends callers to agents with the right expertise.
SIP ALG: SIP Application Layer Gateway — a router feature that can interfere with SIP; often disabled for VoIP.
STUN: Session Traversal Utilities for NAT — protocol that helps VoIP traverse firewalls.
TLS: Transport Layer Security — encryption for SIP signaling.
SRTP: Secure Real-time Transport Protocol — encryption for the media (voice) stream.
WebRTC: Browser-based real-time communication standard used by softphones and video.
Number Masking: Displaying a proxy number instead of a user's real phone number for privacy.
Ring Group: A set of extensions that ring together, in sequence, or in rotation for inbound calls.
Hunt Group: A ring group that hunts through extensions in a defined order until one answers.
Auto Attendant: An automated greeting that routes callers via keypad or voice — a simple IVR.
PII: Personally Identifiable Information — data that must be protected under GDPR, HIPAA, and other laws.
BAA: Business Associate Agreement — a HIPAA contract between a covered entity and a vendor handling PHI.
PCI DSS: Payment Card Industry Data Security Standard — requirements for handling cardholder data on calls.

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