How do vending machines distinguish the kind of bills and coins ?

When we buy beverages at a vending machine, we never say "I will insert 100JPY(Japanese Yen) coin".

How do vending machines distinguish the kind of bills and coins ?

Actually, inside vending machines there are machineries that can distinguish the kind of bills and coins.

In the case of coins, their sensor checks materials, diameter, thickness, weight.

Each JPY coins have differnt materials, diameter, thickness, weight, so their sensor can distinguish it easily.

What is more, their sensor also has the function to check whether the coin is fake or not.

If the coin is fake, vending machine return the coin.

In the case of coins, similarly the sensor check the horizontal length of bills.

All JPY bills have same vertical length. but each of them have different horizontal length.

To distihnguish whether the bill is fake or not, JPY bills have various devices.

When they are exposed to light, their color changes. And they have a watermark.