What are SIP Phones?

Simply put, a SIP Phone is a phone that uses the Open Standard "SIP" to set up and manage phone calls. The actual voice is carried over an IP-based network using another Open Standard called "RTP". 

Since these protocols are generically termed "VoIP" (voice-over-internet-protocol), these phones are also sometimes called VoIP Phones, VoIP Clients or IP Phones.

SIP Phones can be classified in 2 main categories:

  • Hardphones, Deskphones or Hardware?
  • Softphones or Software?

Hardphones / Deskphones

Hardphones

A hardphone looks like a regular telephone and indeed behaves like one. However, the hardware is built using network-aware, or more specifically, IP-aware components. The hardphone will connect to an IP-Network using regular ethernet cables or using WiFi. Cordless hardphones are also available, and these devices take another industry-standard cordless technology called DECT, so that the phones communicate with a base station using the DECT protocol, while the base station communicates with an IP-PBX using SIP and RTP as their transport protocols.

Softphones

3CX Softphone Apps

A Softphone is quite simply what its name implies – a software program that provides IP telephony functionality. Again, a softphone will, just like a hardphone, use the Open Standards protocols SIP and RTP for call setup and voice delivery. Any computing device such as:

  • Desktop computers (Windows, Mac, Linux).

  • Tablets (Android, iOS).
  • Smartphones (Android, iOS).

…can run softphone programs, providing a very wide array of options from which to choose. Any computer or smart device that has a microphone and speakers (or a headset) can double up as a softphone. The only prerequisite is an IP-based connection to a VoIP Provider or a SIP Server, often in the form of an IP-PBX.

What are the benefits of a softphone?

Using a softphone allows us to make better use of computing resources, but a more important benefit is actually the fact that it is software-based. Being software-based means that the softphone receives regular updates, ensuring ongoing security and reliablity. Softphones can be integrated with other systems such as CRM systems to help further improve team productivity.

3CX can be used with most popular hardware IP Phones, but also comes with a completely FREE software-based SIP Phone, with extended functions that are not possible to achieve with a hardphone:

Softphones allow for integration with CRM systems, enabling agents to access customer data directly during calls. They also offer mobility, as they can be used on smartphones, tablets, or laptops, allowing users to make and receive calls from anywhere with an internet connection. Finally, softphones support instant messaging, video conferencing, and file sharing within the same interface, creating a unified communication experience.

Choosing a SIP phone service provider

When choosing a SIP phone service provider, businesses should ask themselves the following key questions:

  1. Does the hardware SIP Phone work seamlessly with your phone system?
    Ensure that the SIP Phone you choose - in the case of a hardphone or deskphone - works seamlessly with your IP PBX. Most PBX vendors have supported IP Phones which plug ‘n’ play with the phone system.
  2. Is the provider cost-efficient?
    Consider whether the provider offers a pricing structure that aligns with your budget while providing the features your business needs.
  3. How flexible is the service?
    Ensure the provider offers scalability and adaptability to grow with your business and accommodate changing communication needs.
  4. Does the provider prioritize data security?
    Verify that the provider has robust encryption and security protocols to protect sensitive communications.
  5. What level of customer support is offered?
    Opt for a provider with 24/7 customer support, ensuring quick resolutions to any issues.

Choosing 3CX ensures cost-effective, secure, and flexible solutions backed by world-class support.

Your questions answered…

We’ve answered key questions about SIP Phones and their function. 

SIP stands for Session Initiation Protocol, a communication protocol used for initiating, maintaining, and terminating real-time voice, video, and messaging sessions using Wi-Fi. SIP is the foundation of IP phones, which connect to VoIP systems, enabling businesses to make and receive calls via an internet connection with a wireless headset rather than with traditional phone lines.

While SIP Phones and VoIP phones are related, they are not exactly the same. VoIP (Voice over Internet Protocol) is a broad term that refers to any phone system using the internet for communication, while SIP (Session Initiation Protocol) is a specific protocol used to manage these communications that include voice calls and video conferencing. Essentially, all SIP Phones are VoIP phones, but not all VoIP phones use SIP. A SIP device provides a more flexible, cost-efficient solution, ideal for businesses needing scalable communication systems.

To use a SIP IP phone, connect it to the internet through a network cable or Wi-Fi. Once set up, it registers with your business’s SIP-enabled VoIP provider, to make and receive calls via your phone system, such as 3CX. SIP Phones work just like traditional phones but offer advanced features like call forwarding, conferencing, and voicemail. You can also manage settings directly on the device or through a web portal.

A SIP Phone is a physical or software-based device that uses Session Initiation Protocol (SIP) to make and receive calls over the internet. In contrast, SIP trunking connects a business’s IP PBX system to the internet, enabling voice communication via VoIP. While SIP Phones are the tools used for making calls, SIP trunking serves as the backbone that links your IP PBX to the public telephone network. Together, they create a cost-efficient, scalable solution for any modern business.

To ensure maximum reliability from your SIP phone, you should start by choosing a high-quality internet connection with sufficient bandwidth to handle VoIP traffic. Implement Quality of Service (QoS) settings to prioritize voice data, ensuring smooth communication even during peak usage times. Regularly update your firmware and software to maintain security and performance. Lastly, consider a reliable SIP trunking provider for added stability and ensure your IP phones are properly configured. These steps will help you achieve optimal performance and uptime for your business communications.

Further reading

Last Updated
This document was last updated on 4 July 2025
https://www.3cx.com/pbx/sip-phones/