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Session Initiation Protocol: The Next Big Thing in Cloud Telephony

Session Initiation Protocol (SIP) is a cloud-based service delivery system gaining traction in the telephone technology world. Here's an introduction to appropriate applications for SIP, features on SIP phones and the cost of ownership.

Panasonic's KX-UT670 SIP phone features a 7-inch touch display, 6 SIP accounts, 3-way conference call support, 2x GbE ports, PoE and more.
Fred Harding · December 23, 2013

Telephones continue to evolve, and the latest offering starting to get traction is Session Initiation Protocol (SIP).

Traditional telephones operate off of a pair of wires that the telephone service provider delivers. If you need three phone numbers, you have three pairs of wires.

SIP is a cloud-based service delivery system, so a reliable high-speed Internet connection and a service provider are required, along with appropriate hardware, to make and receive telephone calls.

Some of the things to know as you explore SIP telephony include installation, number of incoming lines, voice messaging, call forwarding, number of on and off-premise extensions and service agreements.


As with any type of installation, I recommend fitting the appropriate tool to the job. Not every application makes sense for SIP telephones, but many do. Think of SIP telephones as similar to telephone systems but with the processing being done online as opposed to an enclosure on premise.

SIP telephony makes sense in small-to-medium-sized applications. Interestingly enough, you can deploy some KSU (Key System Unit) telephone systems using SIP connections for situations where a large number of extensions might be deployed, or with legacy phones that interface with the new KSU.

Installation is through the network. Your signal needs to have a moderate- to high-speed connection to function, and better quality networking equipment is recommended to maintain Quality of Service capabilities. You’ll connect each SIP telephone into the switch, and once programmed and configured, you’ll be good to go.

Clearly, you’ll need to size the switch to the number of extensions. Traditional network distance limitations hold true here: You can have up to 100 meters of Cat wire between the switch and the SIP telephone.


The SIP telephones come from a variety of manufacturers. Since most SIP applications are business-oriented, the telephones tend to have lots of function buttons on them in addition to the normal numeric keys.

As you step up in the options, you’ll find that you acquire features like soft buttons (useful for intercom and speed-dial assignments), larger LCD readouts, more SIP account numbers, and even the ability to interface with control systems and IP cameras.

Features that are commonly found in KSU systems appear on SIP systems, including:

  • Voicemail
  • Caller ID
  • Compatibility with wireless headsets
  • Conferencing, extension and or line in use indication lights
  • Multiple ring tones

Additionally, you can have extensions linked together in different parts of the world, so incoming callers to a number can be answered by someone in Paris or Maiden Rock, without the caller knowing. And if the Maiden Rock extension needs to, they can transfer the call to the Paris counterpart with a couple of button pushes. SIP door stations are available to afford front or back door communication options as well from several manufacturers.

Cost of Ownership

The real reason why SIP telephony is catching the attention of business owners is the cost of ownership. We already understand the equipment costs will be lower than a traditional KSU system, because there is no KSU involved. The cost per phone line is also lower, depending on which service provider you choose to enroll with.

Some of the service providers offer a flat rate fee that covers all the services needed, while others charge on a per-minute basis. Applications will determine which makes more sense for your client. Typically, the cost per phone line is under $50, which compares quite favorably to what traditional phone companies charge for business telephone line service. Add to that equation some of the features available, including no additional charge long distance, integration with cell phones, more advanced voicemail functionality and it’s a persuasive argument.

Where it gets even more interesting is that some of the service providers working with some of the telephone suppliers are offering residual income opportunities for the installer. Clearly, there are few things in the world more fun than going to the mailbox and getting a check each month for work you did three years ago. Industry statistics indicate that people who subscribe to SIP telephone service providers tend to stay with them; one provider says that they have a 3 percent attrition rate per year.

Clearly, there a lot of details that need to be examined when it comes to telephone system deployment. SIP telephony is one of the disruptive technologies installers have available to use, and it makes sense to explore those details in all sorts of ways.

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  About the Author

Fred Harding is in sales and technical support at Capitol Sales, a full service distributor of electronic installation hardware. He is a frequent contributor to CE Pro, writing hands-on product reviews and technical tips. Have a suggestion or a topic you want to read more about? Email Fred at fharding@capitolsales.com

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  Article Topics

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