The following paper describes a prototypical knowledge-based simulator for electronic circuits supporting the user during various phases of the task. The system has been built by augmenting an object-oriented modelled simulator by direct manipulation techniques and by representing knowledge about the simulation process and the application domain in an expert component. The direct manipulation interface enables the user to manipulate the familiar objects of an electronics laboratory via a mouse on the screen. The expert component provides adequate simulation parameters, answers questions about the application domain, and gives examples and partial solutions concerning the user's current problem.