BT lines vs virtual VoIP lines

By Alan
New to VoIP

BT lines vs virtual VoIP lines

In this article we look at the difference between an analogue BT phone line, and virtual telephone lines on a VoIP telephone system.

Analogue or ISDN BT lines

Businesses that use analogue lines or ISDN will be aware that these lines are only designed to make or recieve 1 call at a time.  ISDN pairs will take 2 calls at a time, as they use 2 lines.

The net result of this is that when using analogue or ISDN telephone lines, users need to estimate the amount of traffic that will be carried in terms of simultaneous calls, and have enough lines to handle that much traffic.

Conversely, you might overestimate the amount of lines required, and pay for lines you never use or need.

If all of your BT lines are in use and another caller attempts to call in, then they will normally receive the engaged tone.  Callers wishing to make another outbound call when all of the lines are busy will not be able to do so, and will have to wait for a free line to become available.

Virtual VoIP lines

Virtual telephone lines work differently from analogue or ISDN lines.  Virtual lines do not require a dedicate copper cable, but run over the broadband connection.

Virtual VoIP lines are more flexible than BT analogue lines or ISDN because they are dynamic, so are only open for use when you need them.

Virtual VoIP lines from vivi® are also more flexible than many other VoIP carriers as we do not limit the amount of lines available per customer.  Your available bandwidth on your broadband connection is the only thing that will limit the number of lines available to use.


Call Quality

High quality virtual telephone lines use a bandwidth of 90k upload and download speed on your internet connection to carry a call.  This means that you only need 90k of available speed on your broadband connection in order to make a high quality call.

The quality of a call can be measured in data speed.  Please see the following example of data speeds for VoIP, landlines and mobile phones.

  • 90k – VoIP (High quality)

  • 64k – ISDN

  • 33k – BT analogue line

  • 32k – GSM mobile phone

This illustrates that high quality VoIP connections are actually of higher quality than standard BT lines and ISDN.  vivi® provides high quality VoIP calls which surpas traditional telephone line quality.  

Low call quality using VoIP is normally associated with a poor installation or using a router that is not optimised for VoIP – see our information on VoIP installation advice and VoIP routers.

Reliability of VoIP

VoIP is not a new technology, it has now been around for a long time, and most businesses using VoIP agree that VoIP is a reliable substitute for BT landlines.

The reliability of VoIP can be dependent on several different things.  Please find out more by viewing our document on the reliability of VoIP here.

About vivi®

vivi® own and operate a cloud based business VoIP phone network and have been delivering communications solutions since 1996.

Last updated Tuesday 24-2-2015 5:00pm


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