Both types of waveform arm take the items returned by the network and event arms and generate the necessary requests to retrieve seismograms. The data received are then processed. The regular waveformArm takes each channel from the network arm and runs it through its subsetters and processors individually. The waveformVectorArm takes the channels from the network arm, groups them as motion vectors, three orthogonal components, and runs them through its items as a group.
<waveformVectorArm> <phaseRequest> <beginPhase>ttp</beginPhase> <beginOffset> <unit>SECOND</unit> <value>-60</value> </beginOffset> <endPhase>ttp</endPhase> <endOffset> <unit>SECOND</unit> <value>360</value> </endOffset> </phaseRequest> </waveformVectorArm>