Heartbeat system

A method of generating a heartbeat signal for an application comprising one or more objects (32,34,36) that may enter a halt state is described. The method comprises: sending a status request (92) to a defined interface (38) on each object (32,34,36); and monitoring responses to the status requests (92) to ascertain if each object (32,34,36) is operating normally or in a halt state. The method further comprises: generating an application valid signal (96) in the event that each object (32,34,36) is operating normally; transmitting the application valid signal (96), if generated, to a monitoring component (50) independent of the application; and generating at the monitoring component (50) a heartbeat valid signal (100) in response to receipt of the application valid signal (96).