SIP Phones and SIP Trunking 

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SIP trunking helps businesses save money by using their existing intranet or internal communication system to access both the internet and outside phone lines.   This system replaces a traditional phone system.  SIP Trunking directs incoming and outgoing calls or data to an internet phone provider or the company’s private network.

The Basics of SIP

SIP is an acronym for Session Initiation Protocol. SIP gives users control over information sent from a Private Branch eXchange (PBX) through an Internet Protocol (IP). The IP can be either an internet address or Voice over Internet Protocol (VoIP).  It also takes information from an Internet Telephony System Provider (ITSP) and tells the PBX where to direct the information.

When communicating with a business’ PBX, the SIP:

  • Keeps up with the location of each line

  • Tells the ITSP and the PBX the expected action (ring this phone line, send this busy signal)

  • Determines if a line is free, in-use or unavailable

  • Directs information where it is supposed to go (i.e. voicemail, call waiting, fax etc.)

  • Tells a phone system which number was dialed and from where

  • Allows both systems to know when a call has ended or been transferred

For external calls, usually a public switched telephone network (PSTN) handles these parameters for businesses and residences.  Having a system that keeps up these parameters lets a business do more with their existing system without paying more.  

Using a SIP Trunk Increases Productivity

SIP trunking increases productivity by adding more functions to an existing system. With SIP trunking, businesses can:

  • Make calls from their intranet, including local and long distance

  • Send emails, text messages and videos externally

  • Conduct internet searches on their existing system

  • Have access to directory assistance and emergency 9-1-1

Without a SIP trunk, a company’s intranet is only able to communicate inside the company unless it uses a PSTN’s hardware (PRIs). With a SIP trunk, a company uses VoIP to connect to outside networks using their phone system.

SIP Trunking Doesn’t Require Extensive Equipment

This service requires a VoIP phone system that understands the information provided by the trunk.  Older analog systems can still connect using a SIP gateway, but the business would not get the full benefit of the SIP.  SIP gateways translate information into contexts an analog phone system understands.  Since the protocol provides real time data information, such as video images, caller ID or call waiting ID, businesses miss out on these benefits by using analog systems.

Businesses need a router capable of prioritizing information presented by the SIP.  The router not only connects the system to the internet, but it also determines what goes first — phone calls or emails.  A router that sends information on a first come first serve basis does not take into account that text messages or other data are not as important in real time as conference calls.


Companies that have a PBX with a SIP trunk can use their system to connect to an ITSP.  If this investment has not been made, the ITSP can host a full-featured PBX.  In some cases, companies with a PBX but few users can affordably switch to a hosted PBX and avoid maintenance, monitoring and manpower required to keep up the system.


Packetworks Solution

Packetworks is your solution for SIP phone solutions and SIP trunking. We specialize in creating the best network for your business’s specific needs. Contact us today to find out more.

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