For 'grounded' plugs, flat blades (see previous tip), but with round grounding pin plug and receptable with side grounding contacts is used (see picture)
An adapter will allow you to plug an appliance designed for one type of outlet into another type of outlet. Despite the fact that more than a dozen different types of plugs are in use, a typical travel adapter kit usually contains about five adapters which are capable of dealing with most of the outlets shown here. Adapters often manage this versatility by bypassing the ground/earth wire.
Beware : an adapter by itself will not change the electrical voltage. You must be sure that your appliance can handle different voltages (either automatically or through a voltage switch). If it can't, you will need a voltage converter.
In case you want to bring any electrical appliances with you, here is the system the USA uses : 120 volts and 60 Hz. It is a flat blade attachment plug (see picture)
The two-blade plugs are often polarized, with one blade larger than the other. Most outlets are designed to handle these. The larger blade is the neutral side of the current. This is a safety feature intended so the plug can be inserted one way only to reduce the chance of accidental shock. If you try to plug a modern plug into an old-style receptacle for equal size blades, it won't go in unless you file down the larger blade to the older plug size.