When you have bought your groceries, you must pay for them. The bill appears on the vision desk below the vision phone. It is important to check the bill because computers can make mistakes.

When you are satisfied the bill is correct, you dial your bank number. It is printed on the bill at once. You sign the bill by placing your thumb on the vision desk alongside the bank number. An electronic thumbprint is taken and transferred onto the bill.

Signing bills in this way stops anyone else from using your bank number. No two people have the same thumbprint.

The bill is finally sent to the bank which pays the shop the money owned.

Note: Sounds like a good system to me!