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SIP Phone - What is it and How does it work?

September 29, 2022 | 3 Minutes Reading

Chances are, you have already heard the word ‘SIP Phone’ thrown around a lot. That is because the SIP Phone is rapidly gaining popularity in the business world due to its cost-efficient features. But should you switch over to SIP technology or not? To answer that question, let us first understand SIP and how SIP Phones can benefit your business.


What is SIP?

SIP is an acronym that stands for Session Initiation Protocol. SIP is a protocol to initiate an IP communication session using IP devices on an IP Network. In simpler words, SIP is a signaling protocol to set up or establish an IP communication session. It is a way to communicate over the internet rather than a traditional PSTN (Public Switched Telephone Network) line.

Think of it like a rule book, which tells the signal about:

  • locating the party;

  • encoding and decoding media using the appropriate codec;

  • defining how to construct and send signaling packets; and

  • setting up and managing the calling feature.

SIP technology is most frequently used for Voice Over IP (VoIP) services. However, it is also commonly used for other types of communication as well, including video calls and instant messaging. VoIP or business phone systems provide the transmission of audio and video communications through internet networks.


SIP and VoIP often go hand-in-hand. However, they are not the same. Let us take a look at some fundamental differences between them:

VoIP (Voice over Internet Protocol)

SIP (Session Initiation Protocol)

It refers to any internet-based phone service.

It is a signaling protocol for maintaining communication sessions for most VoIP deployments.

VoIP carries media in the form of sound over an internet network. 

SIP can transfer all forms of multimedia over the internet, hence, making it more flexible.

VoIP is a layer 3 network protocol.

SIP, on the other hand, is a protocol through which VoIP is facilitated.

SIP Phones: Explained

SIP Phones are telephonic devices used to establish communication over the internet using SIP technology. These phones use the internet network to place and receive calls, in contrast to traditional phone systems that are dependent on physical cables and network towers. As a result of this, they are also substantially safer and much more dependable than conventional phones. SIP phones can run without a computer, making them perfect for a business setting. All they need is a reliable broadband connection.

 How do SIP Phones Work?

SIP phones function the same way you would use the internet on any other device at the most fundamental level. 

When a call is made from a SIP phone, it alerts the SIP server it is linked to, which is typically the company VoIP service. SIP server next establishes a communication with a different extension or transfers the call to the Public Switched Telephone Network (PSTN). The call is established when the phone on the other end is answered. SIP phones automatically, and in real-time, negotiate the status and quality of the call.

This stands in stark contrast to a conventional phone system, which consists of two components: a PBX (private branch exchange) for call management and PRI (primary rate interface) lines for connecting calls to the PSTN for call routing.

With SIP, a virtually deployed SIP trunk connects to the PSTN through the internet, doing away with the requirement for PRI lines. The fact that SIP-based telephony requires so little infrastructure, hardware, and equipment stands out above all and is the main reason businesses are looking to adopt them.

Types of SIP Phones

There are two main types of SIP Phones present in the market today, namely:

  • Virtual Phones

  • Physical Phones

Software-Based SIP Phones (Virtual Phones)

SIP phones that are software-based enable you to make phone calls over the internet using a computer by installing software programs on your desktop or laptop. Many softphones are offered, including Wengo, XLite from Counterpath, and others.

Hardware-Based SIP Phones (Physical Phones)

Hardware SIP phones provide the same functions as conventional phones, but instead of using PSTN lines to place calls, they use an IP network. SIP phones do not require a separate internet connection because they can share your computer's current data network. 

Physical phones vary widely from one another. Therefore, they can be classified into basic, intermediate, and advanced categories.

Basic: These SIP phones are used by call center, or contact center employees and are regarded as almost a starting VoIP phone. These phones can make both internal and external phone calls and contain a dial pad.

Intermediate: Intermediate SIP physical phones offer a greater range of features, frequently including a browsable directory with numerous extensions. These phones are frequently used by the entire workforce, and they are also provided to those who work from home.

Advanced: Advanced SIP physical phones frequently have a full-color display, several extensions, Wi-Fi or Bluetooth capability, and can perform any function a basic or intermediate phone can. Executives at companies like these phones because they have a more elegant appearance. Grandstream and Polycom are well-known manufacturers of hardware SIP phones.

Features of SIP Phones

SIP phones outperform traditional phones in greater functionality to manage calls. They are less expensive to maintain because they do not require the same installation procedure as conventional phone lines. Some top features of SIP Phones are:

  • Cost-effectiveness

Using a VoIP phone system can help you save a lot of money. Low monthly costs for VoIP systems translate into additional savings on your phone system that can be reinvested in your expanding company.

  • Scalability

SIP technology expands along with your organization. It is simple to purchase extra phone lines and computer chairs for your technology. SIP calling enables groups to purchase a single channel at a time whenever they require more hardware. Moreover, upgrades take minutes, not weeks, so there is no need to acquire more than you need.

  • Mobility

Since the calls are made over the internet, you simply only have to connect your SIP Phones to an Internet connection to use it anywhere in the world. 

  • User-friendly Performance

SIP calling is relatively simple to set up. You can quickly implement technology across your entire company. Additionally, employing an online management panel makes it simple to maintain your call technology. Several top SIP suppliers also offer training if your staff needs assistance integrating.

  • Integration

Through several android applications already available, some VoIP phones give comprehensive enterprise telephony capabilities integrating your Outlook contacts, CRM systems, and business applications.

  • Continuity

SIP Phones not only provide high-quality calling, but you can also take advantage of the features of SIP Calling. It is easy to transfer calls and forward calls on SIP Phones, which ensures that your business never suffers due to lags in communication. 

  • Easy maintenance

SIP providers give tools that companies can use to easily monitor the quality of their calls. You can monitor your complete communication system in one location. Additionally, if something goes wrong, SIP trunking providers can quickly reroute services. This implies that you receive the dependability that your company requires.

  • Better sound quality:

SIP service providers give customers access to recent audio technologies. Even more functions, like HD voice, wideband audio, and automatic noise-canceling capabilities, may be made available to you by some businesses.

Top SIP Phones 2022

  • Poly CCX 700 Business Media Phone 

This SIP Phone offers high-quality audio and video calls. An award-winning innovation, this phone comes with a colour touchscreen operation with a 7” multi-touch LCD display. With its integrated Bluetooth, two USB ports, RJ9, and EHS connectors, you can easily use headsets to go hands-free. 

  • Grandstream GXV3275

Unquestionably, the Grandstream GXV3275 is a cutting-edge powerhouse in the IP phone industry. This device is ideal for video conferences since it integrates an Android OS inside a typical VoIP phone.

  •  Yealink SIP-T19P

The Yealink SIP-T19P is a great low-cost alternative because it offers three-way conferencing together with a basic and clear display at a reasonable price.

  • Ooma DP1-T

For anyone who wants to make calls while at home, the DP1-T wireless desk phone is a desirable solution. Thirty-two customizable speed dials, a speakerphone with a Do Not Disturb mode, and physical hold, transfer, and conference buttons are among the features. Additionally, you will be able to quickly review your call logs and dial a number again if necessary. You will also enjoy unlimited countrywide calling through the Telo service, as well as support for voicemail, caller-ID, and call-waiting services.

  • Cisco 6821 

Although Cisco provides a variety of hardware, software, and other telecommunications tools, it has recently earned a reputation for providing some of the top VoIP business phones available. Wideband audio capabilities, an ergonomic design, and a high-resolution 3.5-inch grayscale display with white illumination are all features of this phone.

End Note

In conclusion, SIP phones are becoming more and more common as we continue to move towards an increasingly cloud-focused world. SIP phones are being used by both small and large businesses because of their affordability, simplicity, and scalability. One thing is for sure- SIP Phones are here to stay.


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