Business voip voip hardware

How to design an IP phone

lesley hansen on how to design an ip phoneWhat is involved in designing an IP Phone?

Lesley Hansen is UK Marketing Manager of German SIP handset vendor SNOM Technology AG and is this week guest editor of This role of guest editor is one that I have introduced to bring a focus on specific themes and is an enhancement of the “themed weeks” that have become so successful on this blog.

Lesley is a time served veteran of the telecoms industry and SNOM are one of the oldest players in the SIP game. SNOM were there right at the beginning of the SIP industry before commercial services were available. When SNOM introduced their first handset the only other vendors around were Siemens and Pingtel (long since deceased). SNOM and Lesley are uniquely positioned to talk about their subject.

This week Lesley  has at my invitation put together  a series of posts outlining the issues and challenges involved in the design and manufacture of IP Telephony handsets. SNOM are obviously going to get a lot of mentions in this series but the intent is not to be a sales pitch for the company. It is natural for Lesley to refer to her own company’s experience in writing the pieces. In this first post Lesley outlines the areas that she is going to cover this week.  She refers to articles that are coming during the week and to which I will link as they go live. I leave the rest to her…

This is the introduction to a multi-part series of articles looking at the issues involved in designing an IP phone. Founded in 1996, Snom Technology AG manufactured the world’s first SIP Handset and continues today to provide a market leading brand of professional and enterprise IP Handsets. As such we are exceptionally well qualified to discuss the concerns and challenges of designing IP Phones.

What is an IP Handset?

A VoIP or IP phone is simply a handset that uses Voice over IP (VoIP) technology to allow calls to be made and received over an IP network (like the Internet) instead of using the traditional Public Switched Telephone Network (PSTN). The audio signals from the voice calls are digitized into IP data packets, the handset is connected to an IP network and these IP packets are routed through a private IP network or over the public Internet creating a connected voice call.

IP Phones look very much like traditional office handsets but they are based on a different underlying technology. The use of IP Technology raised potential issues of call quality due to the breaking of the voice into small data packets and these have to be managed in the handset design, and since IP Phones interface with VoIP system telephony software, they have to be able to support features and capabilities that were not provided by traditional office phones. This additional functionality makes the user interface more critical to ensure an easy to use and reliable handset. A good quality of design in an IP Phone can make the IP Handset a valuable resource for many years. A poor design can deliver poor quality voice and become an expensive resource to support and a source of much frustration from business users.

Designing to meet user expectations

Users have clear demands. They want their IP Phones to work and they want them to look good. The problems in designing an IP Phone arise when we try to quantify what working and looking good really means. Elegance and simplicity are very important in phone design but must be balanced with practicality and ease of use this is one of the challenges of IP Phone design. (Further Information: Article on Designing for Beauty)

People are very finicky about voice quality in VoIP because they were used for years to the impeccable quality of landline phones.  The standard for voice quality on a telephone handset has therefore been set by the PSTN and this is what we refer to as toll quality voice.

Voice quality was one of the darkest spots on VoIP’s reputation the early years after its introduction. Now there has been much improvement. For toll quality voice to be achieved on an IP Phone the issues created by using a packet based network where there are no inherent controls on the order or speed of delivery of the packets have to be considered in the phone design. Echo, choppy voice, broken voice, buzzing and delayed speech are common descriptions of problems experienced with the early VoIP connections.  Although some of these factors are the result of a variety of factors not all related to the handset itself, the handset design must minimise the effect of each of these. The one of these most attributed to the IP Handset is echo and designing for echo cancellation and control is key. (Further Information:  article on Voice Quality)

Designing for the demands of IT

One of the challenges with an IP Phone is that the handset has to be configured before the phone can talk to the IP Telephony PBX or IP Server, so before the phone can be used. Provisioning is critical, at its core, the provisioning process monitors access rights and privileges to ensure the security of an enterprise’s resources and user privacy. As a secondary responsibility, it ensures compliance and minimizes the vulnerability of systems to penetration and abuse. In a good quality phone design it is possible to configure phones centralised, which saves a lot of time and money in sending personnel to site.

But the demand is not only these during setup, the design should also ensure updating phones or setting special configurations is easy. This is possible because of this centralisation. Auto-provisioning or auto-configuration is the name we give to this easy and time-saving way to configure IP-phones for IP-PBXs. With auto-provisioning, all user information is entered at the central web interface of the PBX or form the IP Phone management software.  Required data includes the MAC address of the IP-phone, the desired extension and the caller ID which is displayed on the called party phone display. The IP-phone receives the configuration over the local IP network. (Further Information:  Article on Designing for the IT Department)

Ensuring IP Telephony is not compromising the Business

The growing reliance on VoIP has reduced business telephony costs, but it also increases their complexity and this needs to be kept in mind in the IP Handset design. Security has become one of the hottest issues in telecom management. IP telephony not only increases the complexity of data networks, particularly in hybrid telephony environments built with equipment from multiple vendors but it increases security risks. For IP telephony management to be effective it cannot focus solely on reporting on network usage, ensuring dial tone availability and managing call quality, it must place an emphasis on security and protecting the enterprise from telephony-borne attacks.

Today telecom managers face pressure to protect the organization from telephony-related threats, and to do it all while cutting costs and improving ROI. Security measures such as encrypting voice services, placing VoIP equipment behind firewalls, and defending against Denial of Service (DoS) attacks are just some of the steps you can take when introducing VoIP into your organization’s network infrastructure.  Other measures include guarding against toll fraud, securing phone records, and protecting the phones. While there is no such thing as a bulletproof VoIP implementation, you can protect your business by selecting IP Handsets designed to provide high quality security to the business. (Further Information:  article on Designing for Security)

No man is an island – and neither is an IP Phone!

Many solutions using IP Phones are hybrids. A hybrid telephony solution could be mixing either IP or PSTN, it could involve a mix of hosted and on premise telephony services and to get the fully set of functionality needed by the business it is likely to include hardware from multiple vendors. Even if an IP Telephony solution is deployed as single vendor, single deployment single technology it is highly likely that over time elements of third party products or new technologies will be introduced.

It is therefore very important when designing an IP Handset that standard are complied with consistently to ensure the IP Phone is able to operate in a mixture of existing and potential environments. Snom’s operates an interoperability program that gives customers the opportunity to find out which components work with each other. To assure the interoperability between the IP Phones and other elements of the IP Telephony solution, all Snom handsets undergo a range of interoperability tests in our labs. Advanced features such as transfer and Music on Hold are required to work. For our partners gaining the Snom Advanced level of interoperability means that the customer can be assured that the tested functionality works smoothly. (Further Information:  article on Designing for Interoperability)

And the final design criteria – cost

The best quality and most elegantly designed IP Phone in the world will not be widely accepted unless it meets the business expectations regarding cost. Cost in its broadest sense will include cost of acquisition, cost of deployment, cost of ownership and return on investment. Any IP Phone design must consider each and every one of these aspects. (Further Information:  article on Designing for the Financial Director)

Snom’s investment in Handset design is significant and over 45% of our workforce is focused on Handset design, testing and development. This approach has made Snom a leader in the market and unique software and hardware developments on the Snom handsets are emulated by many other IP Telephony and Handset manufacturers.

Lots and lots of VoIP posts on – check em out here

Trefor Davies

By Trefor Davies

Liver of life, father of four, CTO of, writer, poet,

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