The time difference between samples having the same sample number but belonging to different signals. Ideally the skew is zero (or less than one sample interval), but in some cases this is not so. For example, if the signals were originally recorded on multitrack analog tape, very small differences in the azimuth of the recording and playback heads may result in measurable skew among signals. If the skew can be measured (for example, by reference to features of two signals with a known time difference), it can be recorded in the `header' file for a record; once this has been done, getvec and getframe correct for skew automatically. If you need to correct for skew, see skewedit(1) and header(1) (in the ECG Database Applications Guide), or see section dbsetskew. Prospectively, if you anticipate that skew may be a problem, it is a good idea to apply an easily identifiable synchronization pulse to all your inputs simultaneously while recording; you can then locate this pulse in each digitized signal and use these measurements to correct for skew.