Glossary: telephony, Teams and contact centre

ACD

ACD (Automatic Call Distribution) is the function that distributes incoming calls to the right queue and the next available agent, based on rules such as skills, language and waiting time.

ACD is the core of a contact centre, and the same distribution is now also used for chat and email.

AI agent

An AI agent is an AI program that holds a conversation with the customer, for example by chat, SMS or phone, answers common questions and hands over to a human agent, with the full conversation, when needed.

The EU AI Act requires that people talking to an AI agent are told so. Read more in the guide AI in the contact centre.

Calling Plan

Calling Plan is the way of connecting Teams to the phone network in which Microsoft itself is the operator and provides the numbers.

It is the easiest to get started with but the least flexible. All the options are compared in the guide to Direct Routing and Operator Connect.

DECT

DECT is the standard for wireless phones within a building, where base stations on the premises provide coverage and the phones are connected to the PBX.

DECT is used where staff are on the move, for example in healthcare and hotels. Read more about Ascom DECT.

Direct Routing

Direct Routing is the way of connecting Teams to the phone network in which calls go through your own certified SBC to any operator.

It gives the most flexibility and is usually needed when Teams has to work with an existing PBX, a contact centre or analogue devices. Read more in the guide to Direct Routing and Operator Connect.

Failover

Failover is when a backup, for example a second server, a second SBC or another operator, takes over automatically after something stops working.

A failover that has never been tested cannot be trusted, so it is tested in planned windows. Read more in the guide Redundancy and failover for telephony.

IVR

IVR (Interactive Voice Response) is the voice menu that answers the call and lets callers choose what they need by keypad or speech, so the call ends up in the right queue.

With speech recognition, callers can say what they need instead of pressing their way through a menu.

Operator Connect

Operator Connect is the way of connecting Teams to the phone network in which an operator certified by Microsoft manages the connection, so you do not need an SBC of your own.

It suits organisations that want to keep their operator and have no PBX that needs to stay.

PMS

A PMS (property management system) is the hotel system for bookings, check-in, check-out and rooms.

The PMS usually has an interface to the PBX, so that features such as wake-up calls and room status work between them. Read more about telephony for hotels.

Voice bot

A voice bot is an AI agent on the phone: it understands what the caller says, answers in speech and transfers to a human agent when needed.

It can handle common questions around the clock, so that your staff have time for the harder cases.

SBC

An SBC (Session Border Controller) is the border control for phone calls over the internet. It sits where your network meets the operator and Microsoft, only lets in calls that should get in, and encrypts them.

Teams Phone with Direct Routing requires an SBC. Read more in the guide to SBCs.

SIP

SIP is the standard protocol for setting up calls over IP networks. It is used by Teams, operators and modern PBXs.

SIP trunk

A SIP trunk is the operator’s delivery of phone lines and numbers over an IP connection, instead of analogue lines or ISDN.

With Direct Routing, the trunk connects to the SBC.

Teams Phone

Teams Phone is Microsoft’s telephony in Microsoft 365. The connection to the phone network is chosen separately: Calling Plan, Operator Connect, Teams Phone Mobile or Direct Routing.

Read more about Teams Phone.

Last updated 25 October 2026.