Since the process of synchronization takes a finite time, in order to shorten this synchronization-specific shifting time, Porsche worked many years on the so called "double clutch transmission" which can be shifted-on-load. When driving in a particular gear, the next higher or lower gear can already be shifted. The real gearshift takes place by opening one clutch and closing another simultaneously. This means that the gearshift in this case is adherent. The figure above shows the design of a double clutch transmission in deaxial design.
The second clutch is connected over a hollow shaft with the gear wheels of the gears 2 and 4, the first clutch over the inner shaft with the gear wheels of the gears 1, 3, and 5. In this way, two successive gears can be shifted simultaneously and in a positively-engaged manner. It is however not possible to shift between the gears on one shaft without a torque interruption, as is the case in regular dual-shaft transmissions.
For sufficient speed and comfort in operating such transmissions, electronic regulation of clutch control and gearshift is necessary. The driver can in addition externally influence this arrangement as far as he wants.