You may select arrivals at stations in either a rectangular or circular region. Regardless of which shaped region you use to choose stations, you must fill in all of the parameters for the region.

If you designate stations by code as well as by region, then arrivals will be selected only at stations that satisfy both criteria. This might be convenient, for example, to retrieve phase arrivals as stations of the Korean Meteorological Agency since all of their stations have codes that begin "KS", but a few stations very far from Korea also have codes that begin "KS".

Regardless of how you select stations, the ISC database server can provide arrivals for no more than 20 designated stations. But if you restrict arrivals only by time then arrival at all stations, possibly many more than 20, will be selected.