Reports changes detected in station metadata: one record per change, carrying the class and detail of what changed, when the change was detected, the station or channel epoch it applies to, and a free-text description of the old and new values. Every parameter is optional; with none, all changes are returned. Different parameters are combined with AND. A parameter that takes a list is a comma-separated list whose values are combined with OR. Network, station, location, channel, class and detail values accept the wildcards * (any characters) and ? (one character). Each parameter may appear once; an unknown or repeated parameter is rejected with 400. Times are ISO 8601 (for example 2024-01-31T12:00:00, 2024-01-31T12:00:00Z or the ordinal form 2024-031T12:00:00) and are taken as UTC when no offset is given. Network codes, 1-2 characters each. Alias: network. Alias for net. Station codes, 1-5 characters each. Alias: station. Alias for sta. Location codes, 1-2 characters each. Use -- for an empty location code. Alias: location. Alias for loc. Channel codes, 1-3 characters each. Aliases: chan, channel. Alias for cha. Alias for cha. Only epochs that start on or after this time. Only epochs that end on or before this time. Must not be before starttime. Only changes detected on or after this time. Only changes detected on or before this time. Must not be before startchange. Change classes, case-insensitive, for example Channel, ChannelLocation, ChannelOrientation, ChannelSensor. Change details within a class, case-insensitive, for example Latitude, Longitude, Azimuth, EndTimeChange, DigitalResponse. A single case-insensitive pattern matched against the whole description text, with * and ? as wildcards; use *text* to match text anywhere in it. Not a list. Return at most this many changes. Must be 1 or greater. Response format. Only xml is produced. The matching changes. A query that matches nothing still returns 200, with an empty Changes element. Invalid request: an unknown or repeated parameter, a malformed network code, a limit below 1, an unsupported format, or a time range whose end is before its start. Internal error, including an unparseable time value.