There are a growing range of broadband technologies that allow you to connect to the Internet and the technical terms can be confusing.
Below is a list of the most commonly used terms, click on each term to reveal a short definition and diagrams to explain what they mean.
Green Roadside Cabinet
Most premises are connected to the existing network by copper telephone lines which are brought together in a green roadside cabinet. The cabinet then connects these lines to the local exchange.
New fibre cabinets house a faster fibre link from the exchange and are often sited close to the original green cabinet to link up with the individual copper lines serving each property.
A telephone exchange is where all the broadband and phone connections of your local area meet and connect to their respective provider’s network. Your distance from the nearest exchange can sometimes have an impact on the broadband speeds you’re able to receive
Fibre to the Cabinet (FTTC)
Fibre to the Cabinet (FTTC) provides a fibre connection between your nearest green roadside cabinet and the exchange. The final leg uses the existing copper telephone line network between your home and the green roadside cabinet. This will still deliver much faster speeds than are available over standard broadband connections.
Fibre to the Premises (FTTP)
Fibre to the Premise (FTTP) is a pure fibre connection from your home to the exchange which can deliver download speeds of up to 330Mbps.
FTTP, which is sometimes referred to as Fibre to the Home (FTTH), is a relatively new technology being rolled out in parts of the Connecting Cambridgeshire intervention area.
Asymmetrical Digital Subscriber Line (ADSL)
Broadband was first launched in the UK in 2000, using a technology called ADSL. Prior to this
‘first generation’ broadband, Internet access was achieved through very slow ‘dial-up’ services, which prevented the making and receiving of phone calls while connected to the Internet.
With ADSL broadband, the broadband signal is carried along the copper cables that connect
your telephone to the local BT exchange, as shown in the figure below. These cables (which can
be underground or carried on ‘telegraph’ poles) may stretch for many kilometres.
Exchange Only (EO) Lines
The vast majority of UK premises are connected to a green roadside cabinet which then connects to the local exchange. However, a small proportion of business and consumer properties are served directly by the local exchange rather than by a green cabinet – so called “exchange only” lines. It can prove more challenging to bring fibre broadband to properties served by exchange only lines.
An all-in-one cabinet is a combined copper and fibre cabinet. The advantage is that rather than installing two separate cabinets only one is required. The downside is that these cabinets cannot support as many connections as the more usual two-cabinet solution so they are not suitable for use in all locations.
BT initially install cabinets with around a third of their total capacity so there is room to increase it where demand is high. The majority of the cabinets have enough room to connect 288 lines. There are also smaller cabinets which can connect 96 lines.
If all lines in a cabinet are in use and the remaining two thirds have also been installed and acquired, an incremental cabinet may be needed to meet the demand of an area.
When an incremental cabinet or a new cabinet to connect premises that are too far from their original fibre enabled cabinet is installed a process called ‘live-to-live’ migration takes place.
This process takes place when premises that are already on existing live cabinets, but need to be moved onto another live cabinet. This is a tricky process for which BT must agree processes and protocols with all Internet Service Providers offering service on the current cabinet and then complete the changeover at a time agreed by all parties so that there is no drop in service for existing customers.
This process can take between 30 and 90 days.
Other Technologies – Satellite, Wireless, Mobile
Connecting Cambridgeshire is rolling out fibre broadband. Visit our Other Technologies page for definitions and further information about satellite, wireless and mobile.