Signals are the basic data exchange units on a vehicle network, and are equivalent to CAN channels.
Each frame contains an arbitrary number of signals. Individual signals that are transmitted (speed or temperature, for example) are often less than the maximum payload of a frame, therefore several signals are typically sent together in the same frame.
Static signals are contained in every frame transmitted, as opposed to dynamic signals, which are transmitted depending on the multiplexer value. A static signal can be used to create a dynamic signal. However, the dynamic signal cannot be changed to a static signal afterward.
A dynamic signal is transmitted in the frame when the multiplexer signal in the frame has a given value specified in the subframe. Dynamic signals may overlap other dynamic signals when they have a different multiplexer value.
A multiplexer signal carries an identifier for multiplexed signals. Multiplexer signals may not overlap other static or dynamic signals in the frame. A PDU can contain only one multiplexer signal.
Multiplexed signals are separate signals that occupy the same bit space in a frame. They are linked by a separate, multiplexer signal that determines which signal gets to occupy that bit space in that particular frame instance. Multiplexed signals are transmitted using the same multiplexer identifier.