Telephone Lines

SIP stands for Session Initiation Protocol. It is designed to set up connections between devices such as computers, phones, PBXs, video conferencing units and servers.

A SIP Trunk is a virtual phone line that connects your phone system to the public telephone network. It sends the data over a data network, instead of over an ISDN circuit. SIP Trunks can be used instead of ISDN circuits to carry all of your telephone calls, or in conjunction with an ISDN circuit to provide a resilient telephony solution.

That depends on how many simultaneous calls you expect to take place at one time. Obviously, this will depend on your business. If you’re running a call centre it could be one SIP Trunk per operator. For more typical companies, you’d usually have one SIP Trunk for every 5 or 6 phones.

Chances are it will save you money. Up front, you’ll need to pay for a direct connection to your SIP Trunk provider (to ensure good call quality). You’ll probably also need a SIP-ISDN gateway.

As soon as the service is live you’ll save money on your connectivity (because the data connection will be cheaper than your existing ISDN circuit rental). You’ll also save money on your line rental and on your calls.

So the switch from ISDN30 to SIP usually pays for itself.

SIP Trunks utilise your existing data connection, thereby negating the need to spend money on monthly line rental for ISDN circuits. Calls sent over the Internet are much cheaper than calls sent over traditional telephone infrastructure, thereby saving on your monthly call costs. Because SIP Trunks are provisioned over your existing data connection, provisioning can be done instantly as you do not need to wait for circuits to be installed.

Unlike with ISDNs where you have a maximum of 30 channels per circuit, a SIP trunk is fully scalable so you can have as many or as few as users as you want.

By retaining one of your old ISDN circuits, you can add resilience to your phone system, thereby ensuring that even if one of your connections goes down, your telephones will continue to work at all times.

PSTN (Public Switched Telephone Network) is also often referred to as POTS or Plain Old Telephone System. This is the traditional copper network that's being gradually phased out with the introduction of NBN. Although still in use by a lot of businesses, PSTN lines are old technology that's being superseded by IP telephony. As Australia’s broadband infrastructure is rolled out, PSTN lines will be decommissioned and services transferred to digital lines and sip trunks.

PSTN lines don't require a telephone system and are often used by smaller businesses or as standalone lines for EFTPOS, Fax or delivery of a DSL service.

 

ISDN (Integrated Services Digital Network) is a form of digital network technology that enables multiple concurrent telephone calls using the one PSTN line. Essentially, this is a form of IP telephony where a special data connection is used to deliver telephone services using the existing copper lines. There are two main ISDN networks in Australia, Optus and Telstra. Although the technology is pretty much the same, there are some differences. The main one being that optus multiline is available in increments of one call lines (ISDN channels) over and above the first ten. Telstra’s ISDN is only available in blocks of ten i.e. ISDN 10, ISDN 20, and ISDN 30.

ISDN lines require a telephone system fitted with a PRI (primary rate interface) card and come with high end features and functions such as extension level billing and multiple direct in dial numbers.