Leased Lines

Connectivity: How To Choose Your Phone Lines

In today's busy world of business, there's always huge amounts of information to digest about what is right or wrong for your business.  If you are looking to upgrade your business phone system, then you are probably focused on the features and functions of the phone system itself.  However just as there is some complexity in your choice of IP or cloud phone system, there are also things to consider regarding your connectivity, or lines from the outside, i.e. which type of phone lines you should purchase.

Leased lines

Leased lines are rapidly becoming the new standard in today's 24/7 connected business environment. A leased line is a permanent, always-on connection between two locations; a dedicated, private line which only carries communications and traffic from your company, resulting in a guaranteed level of service. The line can be used for data, video and voice and is most effective when sharing bandwidth hungry applications between different offices. High-speed connections up to 1Gig are available. When fast internet access is vital rather than simply convenient, leased lines offer a fully managed, symmetric (very high speed in both directions) and not contended service (bandwidth reserved exclusively for your business).

Analog lines

An analog line from the outside is a consumer grade line with a number. The regular phone line which most people have in their home is also an analog line. Your voice is picked up by your telephone mouthpiece and then sent down the phone line as an analog waveform. In other words, your quality varies up to 100% depending on other factors, rather than simply "on" or "not on" as is the form with digital.

Analog phone lines are now a very old style of provisioning and require separate copper lines for each number. Back in the day offices used to have many individual analog lines going into them for many individual analog phones, but nowadays other technologies have largely displaced lines such as these for offices. With only analog phone lines to the outside, there is no point in purchasing a digital or IP phone system as the advantages of these cannot be realised using an analog line.

ISDN2/ISDN2e - 2-8 users

To transmit data, however, it is far more efficient and simpler to keep it in its original digital state. ISDN2 is a digital line to the outside; ISDN2 is the smaller of the type of ISDN connections. The digital nature of ISDN2 allows the use of a variety of services:

  • identification of incoming calls
  • missed call identification
  • call back requests
  • call forwarding
  • call barring
  • malicious caller ID

ISDN2 also permits the addition of DDI extensions: it is possible to add up to 50 DDI numbers onto 2 incoming ISDN2 lines. However, ISDN2 is limited to 8 channels which is why ISDN30 is more appropriate for 8+ users.

ISDN30/ISDN30e - 8+ users

ISDN30 is a higher capacity version of ISDN2, designed for bigger offices with more simultaneous calls. ISDN30 is the connection of choice for larger small offices and is an efficient line technology. Much of the line management (ie adding additional channels) can be organised without the cost of additional engineering visits. Each ISDN30/30e connection/line provides 8-30 independent 64k channels. Any of these lines can be combined for bandwidth hungry applications such as high quality video conferencing or transferring large data files.

ISDN30/30e can be used for creating a wide area network that will link multiple offices together. ISDN30 is supported by most local exchanges so it is available in most areas. Unlike ISDN2 which is limited to 50 DDIs, with an ISDN30 connection, an unlimited number of DDI numbers can be added, allowing anyone to dial directly through to the right department or person without being passed around the company.


By utilising SIP, or session initiated protocol, is a phone line option that differs from analog and ISDN as it is carried over a data network, be it ADSL, SDSL or leased lines. SIP uses a data network but can be partitioned from the data over that network to assure the quality of service (QOS). By utilising your data connection, SIP negates the need to spend money on monthly line rental for ISDN2 or ISDN30 circuits. Calls sent over SIP are much cheaper than calls sent over traditional telephone infrastructure, thereby saving on your monthly call costs. And, with instant provisioning of the service using your existing data connections, there is no need for the installation of ISDN circuits.

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. With SIP, the quality of your connectivity is paramount. Although it is possible to run SIP Trunks over the public Internet, however, we do not advise this as phone calls are sensitive to delay, variations in delay and data loss (aka latency, jitter and packet loss).

If your offices do not use SIP architecture, then your business may be left staring at the great voice and data divide from disjointed phone equipment and data systems and their equally disjointed administration. SIP inhibits the ability to standardise technology across sites for users, desktops and customer features, which can lead to business process disparity from site to site, business continuity management issues and inconsistent service levels for customers, not to mention the expense of maintaining lines between remote office locations.

In conclusion, if you are running a small business or medium enterprise company there's a lot to think about when it comes to phone systems, connectivity, and lines.  Here at Telefonix we have more than 25 years of experience in helping clients make the right choices for their business, with straight-forward and transparent advice.

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