But now I've found Square. Its a little square that you attach to the audio outlet in your mobile phone (I use an iphone). You then swipe the card and fill in the price info on your phone (plus tax if necessary). The person signs on the phone and then you have the choice of sending them a receipt by email or text.
It works brilliantly! It is free and you don't pay any monthly charge. They just add a small percentage on top of the usual credit card percentage. This means that when I don't use it for a few months, I won't be charged anything. After use, the funds are sent to your account that same evening. It accepts Visa, Mastercard and Amex.
If you want to start accepting credit cards (or want a better set up than you already have), you really should check it out. You can also use it to accept cash, so that it keeps all your transactions in one place. You just by pass the credit card swipe part and enter the cash details and send a receipt or not. When you accept cash, Square makes no charges. They then produce good spreadsheets of all transactions accessible either on the phone or on your computer.
The Square is quick and easy to sign up for; I received the Square in a couple of days; and it was easy to get started.
And it works wherever you can get a phone signal. Take a look at Square's website for more info. Let me know if you give it a go.