Packet Tracer Router plus module

The use of packet tracer to do experiments so long, but do not know how to add, also did not pay attention to, today for an experiment need some modules, just remember to add, but when added, but it shows: Cannot add model when the "" is on. Studied the next, as if there is no place to turn off the equipment, is it the use of command? Check it out, there is no such order. So in the open router interface, go to the physical, see a power button, will be this, then point, Yi, unexpectedly is here, alas ...

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