as NDCs. These 21 NDCs provided data from 46 seismological stations in all. The data volumes contributed by the stations are considerably larger than in the 1984 test, which involved only parameter data. A total data volume corresponding to about 60,000 pages of typed information was exchanged during these eight days. This is about half the size of the Encyclopaedia Britannica . Only the future will tell whether our data contain as much valuable information as those prestigious volumes. The procedures for operating an NDC, collecting and compiling seismological data and transmitting such data to experimental international data centres are now well established. All countries which tried to establish and operate a national data centre were quite successful in doing so. This should encourage more countries to engage in the experiment. Broader participation and better coverage of the globe is essential if we are to meet the objectives of GSETT-2. These objectives are, as you may recall, to test the individual components of a modem data exchange system as specified in the Group's fifth report (contained in CD/903), and to test the interaction of these components in a realistic environment - that is, to demonstrate that the system is able to cope with all the seismic events that are observed around the globe. The Group noted with satisfaction that efforts are under way in some 10 additional countries to join the experiment and to establish national data centres. To encourage even wider participation the Group decided to reduce the technical requirements for participation in the experiment. While maintaining that the prime purpose of GSETT-2 was, and still is, to routinely exchange and analyse level II or wave-form data, the Group agreed that countries that today do not have facilities available for the routine exchange of digital wave-form data may participate by contributing level I or parameter 
**Analysis**
The text discusses the Global Seismic Experiment Test (GSETT-2) and the National Data Centres (NDCs) that contributed to the experiment. The text highlights the success of the experiment, the exchange of large amounts of data, and the encouragement of broader participation from more countries. The focus is on the scientific aspect of the experiment, specifically seismology, and the technical requirements for participation.

**Category**
Science and technology