The NSG 200 Plug-in system was developed to simulate the various disturbances, as they occur in practice on AC or DC line supplies. With the aid of interference simulators, components and equipment can be reliably tested on their susceptibility to interference. This makes it possible to take precautionary measures during equipment or component development. Further the system can be used in quality assurance control or equipment acceptance tests. The system consists of a basic unit and a number of plug-in modules, which cover most types of interference (mainly standardised pulses). This construction permits a continuous evolution to meet latest findings in interference techniques and newly issued standards with minimum effort.