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What is VOIP?


VOIP is commonly known as phone service over the internet and stands for Voice Over Internet Protocol. This has paved the way for VOIP telephones

Common Questions about VoIP

  1. How does VoIP work?
  2. Why do companies choose VoIP telphones?
  3. Can I use VoIP telephone systems over my existing computer cabling?
  4. Is my existing computer good enough for a good phone signal and quality?
  5. What are the common problems with VoIP?
  6. What is the cost to upgrade?

How do VoIP telephones work?

Internet protocol was originally designed for data networking and then adapted for voice transmission by enabling the protocols for voice networking. Legacy data and telephone used to be separate installations and terminations. VoIP cabling requirements now require a 4 pair twisted pair data cable for each phone

This means for a VoIP system installation your phone service is delivered over your internet connection compared to the standard telephone wiring previously associated with telephone cabling

Older telephone system would run to a central telephone (PABX) unit and individual telephone cables would then run to each phone socket at the desk locations

Incoming and internal transfer of calls would all route through this control unit

With VOIP telephones all the management is done over the same internet connectivity as your computers

Why do companies choose VOIP?

VOIP telephones are usually chosen for 2 main reasons

  • Reduced costs
  • Increased functionality

It is the increased functionality that a correctly installed data cabling system provides the basis for a fully functioning, problem free phone system

The structured cabling allows the phone to be moved to anywhere in the building with a data cabling port and work exactly the same as it did before.

With legacy phone systems the port the phone was plugged into would have had to be moved along with the phone

Adding VoIP to an existing network

Can I use VOIP telephones over my existing data cabling?

When considering an installation of a VOIP system there are two considerations

  • Will I have my computers and telephones on separate data cabling lines
  • Will I have my computers and telephones on the same data cabling line

Thus a lot of the decision here will be whether it’s a new installation of data cabling or if you are adding a phone system to the cabling you already have. Generally this will influence the ability of adding VoIP to an existing network

Sharing a cable will be slightly less in cost of cables. However the computer speeds will always be limited to the speed of the phone unit it is plugged into.

However is always recommended to install 1 cable for the PC and 1 cable for the phone wherever possible.

Is my existing cable suitable for VoIP Telephones and VoIP system installation?

The VOIP system will require an internet connection type cable so will need to be a minimum of Cat5e with an RJ45 socket such as below

However most new installations now are allowing for a minimum of Cat6 installations and Cat6a systems and beyond. In the same way this is to future proof for 10gig transmission and above. Although VOIP doesn’t use this higher speed bandwidth it its still a consideration when adding VoIP to an existing network. Generally it is best to standardise your structured cabling network to future proof both your PC and Telephone transmissions


Internet Cabling Data Outlet 3

Internet Cabling Data Outlet



Internet Cabling Data Outlet

The data cabling as above will ideally all go to a single cabinet in the building or to a single cabinet per floor which are then linked back to a central communications room.

If the cables are not all centrally run and terminated the ability to move phones and people around the office will be limited.

In addition if the cables doesn’t all link to a common cabinet either directly or through cabinet links then the ability to transfer calls between phone son different networks becomes an issue


Legacy Telephone Outlet 2


Legacy Telephone Outlet


Legacy Telephone Outlet

If the existing phone system is run on legacy phone cabling with BT phone socket outlets then the telephone cabling will need to be replaced with internet standard data cabling.

These sockets are only suitable for legacy analogue transmission and are not suitable or able to be used for transmitting data and therefore able to be used for VOIP phones

If the existing phone system is run on legacy phone cabling with BT phone socket outlets then the telephone cabling will need to be replaced with internet standard data cabling.

Is my existing data cabling good enough for VOIP transmission

For a VoIP system installation your existing data cabling infrastructure may consist of data cabling back to a central point. Specifically the cabling must be terminated onto RJ45 outlets and patch panels. However unless these cables have been installed to the relevant standards of installation and termination then they may cause unknown problems once the VOIP system is installed

Many companies find a false sense of security in that their existing structure cabling is already in place. However they install a phone system on it only to find poor call quality and drop outs. This is because the data cabling was previously installed poorly

When cabling is installed to all relevant standards then a test report for each outlet should be submitted. Without these you will not know if the structured cabling is up to the standard of transmitting data over it

If the test results are not known then a new testing of the existing cabling is highly recommended


Data Cabling-Test Report

Data Cabling-Test Report


The tester will check the tests against pre-set parameters and produce a Pass (Green Tick) or Fail (Red Cross) in the top right corner

Any cables that fail are not suitable for either PC or Telephone connectivity

VoIP telephones and problems arising with poorly installed data cabling

Poor installation and termination of the data cabling will cause the following

  • Echos

The phone will sound like there is an echo on the line or that the sound is very muffled. Users also describe the experience of the other person sounding like they are talking under water

  • Crackling

The conversation will crackle and sound intermittent. It will sound jumpy and inconsistent

  • Delays

The transmission can cause delays so the timing of the 2 people talking is out of sync. You may hear a response after you have continue talking onto the next point

  • Drop Outs

In this case the phone conversation will just drop off and lose the call.

What is the cost of upgrading my existing data cabling network?

This will depend on the numbers of cables being installed, the location the type of building (and ease of installation) and the cabling standard used (Cat5e, Cat6, Cat6a)

As an outline for installation of 20 outlets and upwards £35-50 per outlet for Cat5e and £45-60 per outlets can be assumed. These costs will be confirmed on individual surveys.


About NM Cabling Solutions – Electrical and Cabling Specialist

NM Cabling is a technology and electrical cabling integrator working throughout the United Kingdom.

We have created a comprehensive Knowledge Centre for our industry which can be viewed at

Click for more information on VoIP installations or call us for a no obligation quote 020 7269 4717