Direct Charge Tariff
The case when the call is paid for by the caller.

Digital Exchange
Telephone exchange that operates with digital technology and offers advanced telecommunication service.

Dedicated Circuit
An analogue or digital circuit for data transmission established permanently between two end-points.

Data Communication
The transmission, reception and validation of data between two points by means of transmission according to specific communication protocols. 

Disaggregated Network Elements
Network elements, such as physical locations, transmission and switching capacities, which are considered separately for leasing purposes.

Debtor Operator
A PTO that becomes debtor in relation to another telecommunications operator by using its network to provide telecommunication services.

Distribution Frame
A network element that serves as junction and limit between the external cables and the equipment of an exchange, affording great flexibility for the connection of both parts of the network.

 
Detailed Billing
The indication of each call (except the free calls), the number of calls, the called numbers, the time and duration of calls and their respective tariff units.

DUCT 
Conduit for installation of cables, between the external cables and the distribution frames.

packet transmission and telemetry.

Direct Access
Situation in which the client is connected directly to a PTO (Public Telephone Operator) by physical line, optical fibre or by radio-electrical means.

Distribution Box
A case mounted on a base or fixed on a wall that contains the connection boards for distribution cables.

Dedicated Line Subscription
A subscription for a dedicated phone line to be used with private telephone exchanges.