SIP Trunking allows service providers to extend it to other applications such as high-definition video/voice, mobility, conferencing, and presence.


SIP trunks are basically used in three broad contexts: 1) as an interconnection option to the PSTN (public switched telephone network); 2) as a SIP port on an enterprise server that offers interconnectivity between different enterprise servers such as telephony, voice mail, presence, etc., and, 3) for SIP interconnectivity between IP-PBXs, replacing traditional TDM (time-division multiplexing) lines. All the signal processing, protocol conversion, transcoding, call routing, quality of service (QoS), authorization, authentication and accounting functions, and switching control to and from gateways are performed by a softswitch or a session border controller (SBC).


Cost Benefits

There is no physical limit to the number of calls that could enter or exit the network at any given time, as SIP trunking allows a customer to oversubscribe the number of voice calls.


Connecting UC Islands

The value proposition of SIP trunking lies not so much in the cost benefits, but in the applications scalability offered by IP networks in general.


SIP Trunking for Call Centers

SIP trunking facilitates next-generation communications applications such as automated outbound voice and telemarketing, event broadcast emails and inbound touchtone order fulfillment.

All plans have set up costs associated with each that can be as low as $100 for the one-time setup and interop testing between our switches. Ask your Sales Engineer for specifics of your SIP connection for exact pricing for interconnection to our switch.


SIP Trunks for Microsoft Lync 2010 and 2013 Users

Carolina Digital offers three different SIP Trunking options:

Unlimited Usage SIP Trunks Service $24/per channel/per month per SIP Trunk. (minimum 10 required). Term-commitment 24 or 36 months required.

There is never a charge for a call inbound or outbound calls anywhere in the United States.

  • Telephone numbers (DIDs) are billed at $1.25/each/per month. Discounts for large volume DID customers.
  • Telephone numbers (DIDs) are available nationwide and from 60 different countries (pricing varies by market)
  • Additional $1.50 per month for E-911 service per location is required.

Business SIP Trunks Service $10/per channel/per month for inbound routed calls from our Tier 0 and Tier 1 Markets.


Ask your Sales Engineer what your local numbers are and they can determine the Market Tier. We have more than 6,500 rate centers in the United States that are Tier 0 or 1.

  • Minimum commitment for this service is 10 channels.
  • There is no per minute charge for inbound calls in our Tier 0 and Tier 1 markets.
  • Cost for all outbound calling is 1.5 cents per minute anywhere in the US and Canada. Per minute discounts offered for large volume customers.
  • Telephone numbers (DIDs) are billed at $1.25/each/per month. Discounts for large volume DID customers.
  • Additional $1.50 per month for E-911 service per location is required.

Call Center SIP-TRUNKS are no cost per month. This plan is designed for very high volume call center applications.

Call centers may have hundreds of SIP-Trunks and this plan allows for Unlimited SIP-TRUNKS with all calls billed based on usage of minutes.

Minutes are billed starting at 1 cent per minute for inbound calls and 2 cents per minute for outbound calls. Minimum commitment for this call center connection is $300/per month.

  • Discounted pricing available for high volume users.
  • Additional charge for DID and E-911 service.

Please ask your sales engineer for special pricing.

Microsoft Lync Server 2013 is designed to take your business’ collaboration environment to the next level.


SIP trunking provides substantial cost savings. 

Lync Communication software connects your employees through features such as: conferencing, presence, and instant messaging at the enterprise level.  Lynx can function on either a traditional telephone line connection or a Session Initiation Protocol (SIP) Trunk provider.  However, SIP Trunking is a next-generation communication platform, which is superior to traditional telephone lines as it provides a salable voice solution that can be adjusted to meet your individual business needs.  Further, SIP Trunking simplifies administration of your network and will save you money on your telecom budget by assuring the solution is tailored to current telephone system needs with up-to-date enhancements to real-time communications.


Carolina Digital Phone offers premier SIP Trunk service for Microsoft Lync that provides a low-cost, high-quality option for Lync servers to connect with Carolina Digital Phone SIP Trunking service.  SIP trunking allows you to consolidate your organization’s connections to a central site.


Long-distance calls are cheaper when placed through a SIP trunk.
Telephone system deployment complexity is reduced, eliminating PSTN gateways as well as their management and associated maintenance costs.  SIP trunking costs are based on bandwidth, which is more easily tailored to the economical increments that make the most sense for your business.  In order to employ your SIP trunking for Lync, your connection must be routed through a mediation server that transcodes media as necessary. This mediation server acts as a proxy between Microsoft’s Lync Server 2013 clients and the service provider. Mediation servers have both an internal and external network interface with the internal interface connecting to the front end servers and the external interface connecting the mediation server to either a public switched telephone network gateway or IP-PBX system. With SIP trunking, the external interface is connected to the ITSP’s external edge.

Over 20 Years Of Service
Our Customers Love Us!

Michael Durdin
Michael Durdin
January 6, 2021.
We love our VOIP phone system from Carolina Digital Phone. The product works like it should and the features are fantastic and easy to use. Also, tech support is top notch. I can't say enough good things about the staff and how quickly they are able to resolve any issues we have had while getting everything up and running. 5 star company!
Jeff Hyde
Jeff Hyde
January 4, 2021.
Our Company has been using Carolina Digital for the last 10 years, before it was Carolina Digital. Great folks, terrific service and we save money every month.
Lisa Nethery
Lisa Nethery
December 18, 2020.
Love working with this team of professionals. They are always pleasant to talk too. Eric and Matt are top notch in support and always willing to help with any issue you have!
Karen Fentress
Karen Fentress
November 25, 2020.
Great, fast, friendly service!
Sylvia Wilson
Sylvia Wilson
October 26, 2020.
The recordings were down for about a week. Eric Lyon had our issue resolved immediately. We are always very satisfied with Carolina Digital!