Phone Numbers, Lines, Extension Numbers, and Users in VoIP
Learn more about what phone numbers, extension numbers, users, and lines mean when they are referenced while using your SpectrumVoIP phone system.
Written by Val Campos
Updated at May 17th, 2024
When you are transitioning from an analog phone system to a VoIP phone system, you may notice some terms used that you have heard of while using your analog phone system. Depending on how your company and previous provider have used these terms, the definition of these terms may differ from how they are used by SpectrumVoIP team members.
Phone Number
A phone number is used by people outside of your phone system to call and speak with people inside of your phone system.
Analog
For analog systems, a phone number is dedicated to a single phone line that is connected to one analog phone. In some cases, a multi-line analog phone or a multi-line on-premise Public Branch Exchange (PBX) can be implemented to allow multiple lines to be contacted.
For example… The example phone number (555) 123-4567 can be called to ring the analog phone that is connected to the phone number's dedicated phone line.
Calling the example phone number (555) 231-6789 rings one line of a two-line analog phone. The agent using this phone can hold their call and use the second connected phone line to call another person.
VoIP
For VoIP systems, a phone number can be designated to a single extension number or routed to multiple extension numbers through a call routing feature, such as a call queue or auto attendant (also known as an IVR menu).
For example… The example phone number (555) 123-4567 can be dialed to reach a call queue that rings multiple agents' extension numbers at once or in a certain order.
One agent has a dedicated phone number: (555) 231-6789. When this phone number is called, this agent is contacted directly.
Lines
Analog
Analog phones usually have a single phone line connected that can host one call. These phone lines are commonly referred to as landlines.
To allow multiple calls to be made at once, additional phone lines can be implemented, although this will incur an additional cost and require an on-site install.
Some analog phone models allow for additional phone lines to be connected. Some companies host an on-premise Private Branch Exchange (PBX) with hardware that manages and facilitates the services of multiple landlines or trunks. Some agents in an analog phone system may have a separate handset that they use to switch lines.
For example… A company has a dedicated IT team that manages an on-premise PBX that uses special hardware to allow multiple lines to be used concurrently.
VoIP
Using a VoIP phone, multiple calls can be handled concurrently as long as the device has available line appearances (also known as lines). In this case, a line appearance is not a physical landline; it is a channel of communication virtually hosted through the phone's interface.
For example… If a VoIP phone has three line appearances, it can display and handle three calls at once.
A user with three line appearances could have two calls on hold while talking with a third caller.
Extension Number
An extension number is a 3–5-digit number that is dialed to reach a specific person within your phone system. Extension numbers allow people inside your company to call and speak with another person within your company without the need for a separate phone number.
Analog
Dialing an extension number for an analog phone rings that phone's dedicated line. Calling an extension number when its line is already hosting a call, will result in the caller hearing a busy tone.
If an agent is using a multi-line analog phone, then one line can be contacted by an extension number while another line is contacted by a different extension number.
If a company is using an on-premise PBX, then different extension numbers may be set to contacts a specific phone or multiple phones.
For example…
VoIP
VoIP phones use a virtual extension number to place and receive calls. A virtual extension can be created and assigned to a seat (also known as a User). An extension number can have multiple devices registered to it.
Some call routing features, such as call queues and auto attendants, also have an extension number to allow calls to be placed or transferred directly to that feature.
For example… When extension 101 is dialed, an agent's desk phone, SpectrumVoIP mobile app, and SpectrumVoIP desktop app ring at the same time.
A call queue with the extension number of 8000 commonly has calls transferred to it by a receptionist. The receptionist does this by dialing 8000 while using the transfer function of their device.
User
Analog
Someone that is using an analog phone is often referred to as a user. Some companies may refer to an agent contacted by an extension number as “User #", with “#” replaced with what their extension number is.
For example… A person using an analog phone that is contacted by the extension number 1001 is often referred to as “User 1001”.
VoIP
When you are using SpectrumVoIP services, the term “user” is synonymous with "extension number". A user is a seat on your SpectrumVoIP account that is able to have VoIP devices registered to their extension number.
The term “user” can also be used to reference a person that is using a device (also known as an end-user).
For example… A business is paying monthly for a seat that is referred to as “User 101”, which can be contacted by dialing the extension number 101.
“User 101” has a desk phone in the office, a desk phone at home, a SpectrumVoIP mobile app, and a SpectrumVoIP desktop app that are all registered to his extension number (101) so that he can use these different devices interchangeably to handle calls.