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Glossary of electronic communication and postal services
AAP - Alternative Approval Process
Fast-track approval procedure of the International Telecommunication Union (ITU) which allows for the approval of technical standards in a short space of time (eight weeks). The AAP was launched in January 2001.Access Time
Time interval between the request of information from a system or a network and the moment in which the same is supplied.Accessory Equipment
Set of devices or equipment associated with the subscriber's terminal equipment, with the aim of obtaining special usage conditions.Accreditation
Act by which an entity which requests it and which acts as a certifying entity, is granted the recognition that it has fulfilled the requisites set out in the legal regime governing electronic documents and digital signatures, for the purposes stated therein.Accreditation Authority
Competent entity for the authorisation and supervision of the certifying entities.Active Satellite
Operative satellite which receives and transmits or retransmits radio communication signals.Address
Identification of a point in a network, at local network (LAN) or WAN level. Although these are generally in digital format (bit sequence), they may also be associated with a more intuitive name (such as ''printer number 2''). They can also identify Internet users for the purpose of exchanging emails.ADSL - Asymmetric Digital Subscriber Line
The most common asymmetrical transmission technology in the xDSL family. An ADSL connection offers a high bitrate downstream channel (1.5 to 9 Mbits/s) and a lower bitrate upstream channel (16 to 640Kbits/s), in addition to normal telephony service in the low frequency range.Aeronautical Mobile Service
In portuguese, Serviço Móvel Aeronáutico (MA). Mobile service between aeronautical stations and aircraft stations, or between aircraft stations, in which the survival craft stations may participate. Emergency position-indicating radio beacon stations may also participate in this service on designated sister and emergency frequencies.Aeronautical Mobile Service (OR)
In portuguese, Serviço Móvel Aeronáutico (OR) (MAOR). Aeronautical mobile service reserved for communications relating to safety and regularity of flight, primarily along national or international civil air routes. OR: off-routeAeronautical Mobile Service (R)
In portuguese, Serviço Móvel Aeronáutico (R) (MAR). Aeronautical Mobile-Satellite service reserved for communications relating to safety and regularity of flights, primarily along national or international civil air routes. R: routeAeronautical Radionavigation Satellite Service
In portuguese, Serviço de Radionavegação Aeronáutica por Satélite (RVA-S). Radionavigation satellite service in which Earth stations are located on aircraft.Aeronautical Radionavigation Service
In portuguese, Serviço de Radionavegação Aeronáutica (RVA). Radionavigation service intended for the benefit and for the safe operation of aircrafts.Allocation (of a band of frequencies)
Entry in the Frequency Allocation Table of a given frequency band for the purpose of its use by one or more Earth or space radiocommunication services, or by the radio astronomy service, under specified conditions. This term also applies to the frequency band referred to.Allotment (of a radio frequency or radio frequency channel)
Entry of a given frequency channel in a plan adopted by a competent conference, for use by one or more administrations for an Earth or space radiocommunication service in one or more identified countries or geographical areas and under specified conditions.Alternative Approval Process (AAP)
Fast-track approval procedure of the International Telecommunication Union (ITU) which allows for the approval of technical standards in a short space of time (eight weeks). The AAP was launched in January 2001.AM - Amateur Service
Radiocommunication service for individual training, intercommunication and technical investigations carried out by amateurs, that is, by duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest.AM - Amplitude Modulation
Type of modulation, in which the amplitude of the carrier wave varies in function of the signal transported. It is used, in particular, in the radio broadcasting service in the 526.5-1,606.5 Kilohertz (KHz) frequency range.American Standard Code for Information Interexchange (ASCII)
Standardised code used in IT systems and data communications, which codes letters, figures, punctuation and control systems in binary numbers of 7 bits (''0's'' and ''1's''). For example, the capital letter "D" is represented by "1000100" and the number ''5'' by ''0110101''.Amplifier
Device which produces an output signal of greater power than that of the input signal. May be used in telecommunications networks to restore signal levels which have been reduced as a result of attenuation on the lines.Amplitude Modulation (AM)
Type of modulation, in which the amplitude of the carrier wave varies in function of the signal transported. It is used, in particular, in the radio broadcasting service in the 526.5-1,606.5 Kilohertz (KHz) frequency range.AM-S - Amateur Satellite Service
Radiocommunication service using space stations on Earth satellites for the same purposes as those of the amateur service.ANACOM
National Authority of Communications - Is the regulator, supervisor and representative of the communications sector in Portugal (telecommunications and postal sectors), in accordance with its respective statutes, as approved by Decree Law No 309/2001 of 7 December.Analogue
Direct representation of a wave which continuously varies in time (in communications for example, it may reproduce a sound or an image). For example a vinyl record stores information in analogue format, which records the sounds in their original non codified form, through a magnetic support. This contrasts to a CD in which the same recording is codified and is consequently stored in digital format. However, in both cases, it is obviously possible, by means of different equipment, to hear the original recording.Anonymous Call Rejection
Abbreviation: ACR. Service which blocks telephone calls from callers who withhold their telephone number.Antenna
Conductor, set of conductors or other devices which enable the reception and emission of electromagnetic waves though the air.API - Application Programming Interface
Software used to provide access to the capacities of a communications operating system. Interpreted as a set of organised commands, for example, the presentation of a graphic or an image on a screen. The API allows the same applications to executed on different receivers, without the need to rewrite the application for each. In digital television, the API consolidates the operating system of the decoder of the receiver, which enables interactive applications to be managed. In particular it supports the Electronic Programme Guide.Artificial Intelligence
Capacity of determined computer programmes developed to have logic which is similar to human intellectual activity.ASCII - American Standard Code for Information Interexchange
Standardised code used in IT systems and data communications, which codes letters, figures, punctuation and control systems in binary numbers of 7 bits (''0's'' and ''1's''). For example, the capital letter "D" is represented by "1000100" and the number ''5'' by ''0110101''.Assignment (of a frequency or a radio channel)
Authorisation given by an administration to use a radioelectric station at a frequency or a radioelectric channel determined according to specified conditions.Asynchronous Transmission
Method of data transmission in which the information is sent character by character, with time intervals between the same. For this reason a signal is sent at the beginning of the transmission and another at the end.ATM - Asynchronous Transfer Mode
Communications protocol, which allows the transfer of multimedia (data, voice and video) over a single network infrastructure using, low-delay packet-switching and multiplexing technique. Technology chosen to support high-bandwidth ISDN. ATM is also the abbreviation used for Automatic Teller Machines.Attenuation
Weakening of the signal level, as it moves further away from its origin (for example, along a telecommunications cable). It is a particularly well-known and undesirable effect in very long cables, where the signal loses its intensity. The effects of attenuation may be compensated through the use of repeating devices which strengthen the signal level along as its route.« Back
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