For active power management some form of auto-calibration was needed with the capability to read a device's power consumption. Peter undertook a detailed examination of computer power-supply systems. He found that the power being used could vary enormously. Meanwhile, a patent search revealed that a similar device had been patented in Germany but had not proved successful as it was relatively primitive, working with fixed values for the power being used. Peter's solution to the problem was to use some form of programmable integrated chip linked to a software program that monitored the amount of power being used and then used a formula to decide whether to switch the slave sockets on or off. Having produced a solution was one thing; getting it to work was quite another. Development was not without its difficulties. On one occasion the only prototype blew up the night before a vital demonstration to the Energy Saving Trust. Over the course of several months more than 30 electronic prototypes of different designs either blew up or melted before Peter was finally able to come up with one that was stable and functioned effectively. At this point, having taken appropriate legal advice, Peter filed a patent for his intelligent switching device.