A leased line is a (usually) symmetric telecommunications line connecting two locations together. Unlike traditional PSTN lines they do not have a telephone number, each side of the line being permenantly connected to the other. They can be used for telephone, data or Internet services.
In the UK, leased lines are usually available at speeds of 64k, 128k, 256k, 512k, 2Mb and provided to the customer on X.21 presentation. Higher speeds are available on alternative interfaces.
In the US, leased lines are usually presented on a T1 bearer circuit in a number 56k or 64k timeslots. This has advantages over the UK - more than one logical connection can be provided on a single bearer, and upgrades can take place relatively easily. However, the customer must manage their own network termination equipment - Data Service Unit (DSU) or Channel Service Unit (CSU).
