Telephony jargon explained

When implementing or searching for a new phone system for your business, the sheer volume of acronyms and jargon can seem overwhelming. You may even feel completely unqualified to make any decisions without a telephony crash course or getting your IT team involved.

Here at RocketPhone, we see this all too often, but truly believe that with today’s modern technologies, telephony needn’t be thrown into the mysterious black box of ‘IT’. 

Instead, with the availability of softphones (oops a bit of jargon there, but don’t worry we explain further down) on the market today, implementing a new phone system should be as straightforward as signing up for any other piece of software. Think how quick and easy it is to get going with Zoom or Slack or Gmail. 

However, even with new technologies come new jargon terms, so we’ve come up with this glossary to help get you clued up. But don’t worry, we’ve actually written the definitions in a way that makes sense and not just more jargon!

with today’s modern technologies, telephony needn’t be thrown into the mysterious black box of ‘IT’


Auto-attendant is a standard feature for most phone systems. It describes the automatic transfer of callers to certain extensions without requiring manual input from a human. An auto-attendant works by providing a simple menu of options for callers to choose from.

For example when calling a company number, a caller may be greeted by a message that reads “Press 1 for sales, 2 for customer service” and so on. The attendant will then automatically route the call to the selected department. 

CTD (Click to Dial)

CTD refers to the ability for softphone integrations or plugins to make any number in an application ‘callable’. For example, with a CRM integrated softphone, you can click a contact’s number which will initiate a call. Think of it as a hyperlink but for calling!

CTI (Computer Telephony Integration)

This may sound fancy but actually all it really describes is voice/phone software that integrates with other computer applications such as your CRM or contact centre software. 

For example, when choosing a CRM, it’s advised to ensure that it permits “CTI” so that you can call contacts directly from the CRM without having to note down the contact’s number and enter it into your deskphone. 

DID (Direct Inward Dialing)

DID describes the action of calling a phone number that directly connects to another phone without having to go through a system’s attendant (menu options). 

For example a sales person may give a prospect their DID number so that the prospect doesn’t have to waste time navigating the company's switchboard every time. 

Hunt Group

A hunt group is a phone system feature that routes an inbound call to a group of members all at once. For example, when a caller rings a company number and passes through to a certain department, the hunt group will ring all team members in that department at once. The first person to answer takes the call. 

IVR (Integrated/Interactive Voice Response)

IVR is a phone system feature that detects voice responses when answering inbound calls. 

For example, when a customer calls into a company’s customer service number, they will be greeted by a recorded message asking the customer to describe their problem. The IVR, using NLP (sorry more jargon but we get to it later) analyses what was said and passes the customer to the right customer service agent to deal with their specific problem. 


In terms of voice communication, Jitter describes small intermittent delays between data, in the form of voice, being sent across networks. Jitter causes voice data to be sent at irregular intervals which can be very disruptive to live calls and will typically result in periods of silence or garbled sound. 

Jitter is typically caused by signal interference or too much data trying to pass through a network. However with internet speeds so good now and softphone systems compressing the voice data load being sent, instances of Jitter are quite uncommon. 


Similar to Jitter, Latency refers to the amount of time taken for a ‘packet’ of voice data to go from one source (phone) to another. Although the delays are usually measured in nanoseconds, a high latency can lead to poor quality calls. 

NLP (Natural Language Processing)

NLP is not something that would have appeared on this list until quite recently. The advance in functionality offered by modern softphones has meant that AI is fast becoming an essential component of voice communication. NLP basically refers to the transformation of spoken language into data, made possible by AI. 

Some of the best softphones available today use NLP during conversations to detect buying signs, offer coaching tips, ensure compliance and much more! 

Number Porting 

Number porting describes the process of taking an existing phone number and transferring it to another provider. This is typically done when you change your phone system vendor and you need to keep your existing phone number. 

PBX (Private Branch Exchange)

Now this is one you might have heard a lot about. A PBX is quite simply the “machine” that routes incoming calls and enables call transferring. It also holds all the functionality of the phone system.

‘Traditionally’ a PBX system was made up of hardware, a team of technicians and usually physically held in a company’s offices. Modern cloud phone systems don’t require any of this and all PBX functionality is handled by software that you never have to see or worry about! 

Predictive Dialer

A predictive dialer is an outbound calling feature that automatically dials numbers from an inputted list. The dialer will call multiple numbers from that list at the same time, passing to an agent only when it detects a connection. It is a feature that can be deployed to get maximum talk-time efficiency out of sales agents. 

Progressive Dialer 

Progressive dialers are much simpler than Predictive dialers but still offer helpful automation. A progressive dialler will progressively dial each number in an inputted list, one by one, passing to an agent once it detects a connection. 

PSTN (Public Switched Telephone Network)

PSTN describes the local, long-distance, and international carriers that make up the worldwide telephone network. In other words, the World Wide Web but for telephony. 

SIP Trunking

SIP Trunking describes how a cloud/internet based phone system connects to the internet through a ‘Trunk’. A SIP trunk combines all of a company’s voice and data traffic into one network. 

SIP Channel

A SIP channel represents one connection to the PSTN. SIP trunks can have an unlimited number of channels, with each channel representing one concurrent telephone call.


A softphone is a software application for making and receiving telephone calls over the internet, rather than a traditional deskphone. Being internet based, softphones can be run on PC, laptop, tablet or smartphone making them perfect for remote or distributed teams. 

Related: Top 10 benefits of softphones


We’ve used the word telephony a lot so it’s about time we actually give it a definition. Telephony quite broadly refers to any technology involving the development, application, and deployment of communication services for the purpose of electronic transmission of voice, or data, between two parties. In fact the term ‘Telecommunications’ is a more accurate term to encompass all our possible communication methods. 

VoIP (Voice over Internet Protocol)

Voice over Internet Protocol (VoIP) is a group of technologies that work to deliver voice and other multimedia over the internet. SIP trunking is one necessary component of achieving VoIP. 

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