ister and predictions of propagation parameters of the emission (such as the transmitter power, the conditions are used to estimate whether any of these frequencies bandwidth that may be occupied and key antenna characteristics) could be used for the new emission without causing unacceptable and the purpose for which the system may be used. The assignment interference to other systems within the national jurisdiction. Simi- of a frequency usually implies an assurance that unacceptable inter- larly estimates are made of the interference that a new receiving ference is not likely to occur and that action will be taken by the station would suffer from established transmitting stations within licensing authority to eliminate such interference if it should occur. the national jurisdiction if its receiver were tuned to a proposed new Typically a fee is charged for the licence, to cover the administrative frequency. When an apparently interference free frequency has been costs of issuing it and a share of the cost of national spectrum found in this way, by inspection, it may be assigned for the new use, details being entered in the national register to prevent further management. assignments being made that would cause or suffer interference in In pursuit of their policy towards industry, governments also the future. regulate telecommunication systems and in particular, the operation Software is available for applying computer methods to the ident- of commercial systems set up to provide facilities for sale to other ification of interference free frequencies that could be used for new parties. Where the telecommunication systems use radio, the regu- systems without causing interference to existing, registered, assign- latory process may be implemented through the issuing, or with- ments. Spectrum efficient use of such techniques, however, requires holding, of licences to operate radio stations. However, regulation the information in the register to be available in database form, of this kind is not discussed here. toget