Abstract: In order to indicate that an event has occurred in conformity with a predetermined protocol, a step involved in implementation of the protocol is selected. An association is recorded with the selected step of a requirement for a trigger signal. The performance of steps comprising implementation of the protocol is monitored, and a condition related to performance of the selected step is detected. A trigger signal is generated, in addition to any signal generated as part of implementation of the protocol, to indicate occurrence of the detected condition. The detected condition may comprise, for example, active performance of a step to generate an output such as transmission of a message, or passive performance of a step to receive an input, or detection that a time interval has elapsed during which the step could be expected to have been performed.