PSTN SIP Connections

If you want to connect regular PSTN services to your Asterisk box, here is a list of connection types. Also, below is a list of companies that provide these services- feel free to add yours.

Basic Business Lines

Often called Plain Old Telephone Service (POTS) lines, provide basic access service and supply a single voice-grade communication channel for single line telephones, key telephone systems, modems and other devices that need to access the Public Switched Telephone Network (PSTN). XO Business Lines offer consistent naming, functionality, standard and optional feature sets and convenient feature packages across all XO markets.


A business telephone system offered from the local central office on a subscription basis. It delivers a set of PBX-like features to individual desks with internal and PSTN access for all the features, functions and applications that a business customer needs. An important benefit of Centrex is that it is a leased or rented service, meaning it is fully outsourced. Service is provided through the Central Office and the customer does not need to invest in capital equipment or worry about maintenance, power, growth, capacity, and/or changes to configuration. Centrex Service offers consistent naming, functionality, and standard and optional feature sets across all markets. This makes Centrex ideal for both regional and national customers looking for an outsourced turnkey business telecommunications solution.

Business Trunks

Connect a customers system to the Central Office to deliver PSTN access with all the features, functions and applications that a business customer needs. Trunks offer shared access, meaning that a number of phone lines can be consolidated on each trunk without any decrease in functionality or service. Trunks, which can be either analog or digital, can carry inbound, outbound or two-way call traffic, can support Direct Inward Dial and any combination of the above. A high volume service, Business Trunks allow customers to reduce the number of connections necessary to support their organizations communications needs. Business Trunks offer consistent naming, functionality, and standard and optional feature sets across all XO markets making it ideal for both regional and national customers looking for a voice telecommunications solution.

three types of Business Trunks designed to support the needs of any customer:

PBX Analog Trunks
Fractional Digital Switched T1 Trunks
Full Digital Switched T1 Trunks.

The ISDN PRI Product

Integrated Service Digital network (ISDN) is a standard, all digital technology that allows simultaneous, integrated voice and data capability over two-wire digital loops and four-wire digital trunks. These loops and trunks access circuit-switched voice and data, data networks and network services databases.

Primary Rate Interface (PRI) is the digital trunking interface using ISDN technology that provides high capacity digital access between the XO Central Office and ISDN-compatible CPE located at the customer’s premise or other service point. The connection is provided through a standard T1 point-to-point, private line facilities.

PRI is configured using a minimum of 23 bi-directional B (Bearer) Channels and one D (Data) Channel (23B+D). Unique to ISDN PRI is its ability to designate this D channel to handle all of the signaling and call control requirements. This functionality leaves the remaining B channels available for any mix of voice, virtual private line, and circuit-switched data.

More than one PRI line can be aggregated so that a single D channel controls up to five PRI lines. In addition, each PRI line can effectively accommodate changing traffic requirements by serving different types of traffic as needed i.e. DID, DOD, Dedicated Long Distance.

How it Works
ISDN uses multiplexing to combine separate data signals together on one digital channel so that they can be decoded at their destination. Since the line is digital, voice conversations are crystal clear.
In addition, ISDN adds capabilities not found with standard phone service:

A digital package identifies who's calling, the type of call (voice, data, etc.) and the number dialed (if multiple numbers, such as fax, are used for a single line).
The ISDN phone equipment decides how to answer the call, and if it's a data call, it makes the connection instantaneously.

Please feel free to add the name of your company here:

  • XO Communications - SIP access via the PSTN nework as well as via our Sonus network. Fractional T1, DS3, OC3 and OC192 access both via the public internet or private connections. Point to point services offered in most US markets.

Created by: lejoneric, Last modification: Mon 16 of Oct, 2006 (17:37 UTC)
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