While the Event server can generally be used independently of the others, there is a strong dependency between the SeismogramDC and NetworkDC services due to the common notion of Channels. The Seismograms returned from the SeismogramDC service contain a ChannelId, which identifies the Channel that the data was recorded on, but the specific information about the channel, such as location, orientation and response, is accessed via the NetworkDC service. Therefore, it is important that the ChannelId returned from a SeismigramDC be the same as the corresponding ChannelId in the Network server. This basically boils down to a requirement that the begin times of the NetworkId, StationId and ChannelId in the seismogram be exactly the same as those returned from the NetworkDC. This enables a client to send a ChannelId from a Seismogram to the NetworkDC and retrieve the Channel and Instrumentation.