The first channel is represented by number 0 and 0xffffffff indicates that this event or interval is not associated with a single channel. This is the time when the recording of the physical signals started. If no time is available, the date alone may be stored as '19930211' or in bytes 0x31,0x39,0x39,0x33,0x30, 0x32, 0x31,0x31. Each channel may have zero, one or several positions, i.e. a channel may appear on several places in a diagram and in different diagrams. A channel may be associated with several single points or with pairs of points, which might be represented graphically as arrows from the first point to the second one.
Several positions can have the same channel number.
For point positions, X1 and Y1 are the coordinates of the points and X2 and Y2 have the special value 0x80000000. For arrow positions, X1 and Y1 are the coordinates of the tail and X2 and Y2 are those of the head. Arrows may e.g. be used to indicate that a channel represents the difference potential between two electrode positions. The coordinates are all inside the CGM VDC extent. Information about the filters that have been applied to each channel may be stored here.