This Recommendation defines the "Continuous Signal support" package of TTCN 3. It defines concepts for testing systems using continuous signals as opposed to discrete messages and the characterization of the progression of such signals by use of streams. For both the production as well as the evaluation of continuous signals the concept of mode is introduced. Also, the signals can be processed as history-traces. Finally, basic mathematical functions that are useful for analyzing such traces are defined for TTCN-3. It is thus especially useful for testing systems which communicate with the physical world via sensors and actuators.