The fischertechnik compressor generates an overpressure of approx. 0.7 to 0.8 bar. The membrane pump is maintenance-free. It is important to use a 9V alkaline battery to provide the power supply to the compressor. The fischertechnik battery set is an even better choice, providing significantly more power than the 9V block and lasting longer, while being rechargeable. The maximum charge time is two hours.