1991 saw again a major overhaul in the train line, in line with the ongoing transition to the new generation 9-volt system that had first appeared in 1986 with the 'Light & Sound' line of sets, with Technic having made the transition to 9-volt the year before. Tracks gained a new appearance with power being transmitted directly through metal strips on the two running rails. The new line abandoned the 12-volt power in favor of the 9-volt system. One of the key weaknesses of the old 4.5V/12V system was the unreliability of the pinned connector plugs, which were notorious for becoming loose or for the wires to fracture over time, whilst the 9-volt system used more positive fitting contacts integrated into the brick studs. The remote-controlled accessories from the 12-volt system however were also abandoned, with only manual point control available and no signaling capabilities. At the same time, the 9-volt train motor was made train-specific by its fixed wheels, while the similarly sized 9-volt universal motor changed from individual metal axles wheel holes to axle holes for Technic axles, for which there were no train wheels available.