There may be no such thing as a new idea but there are almost endless variations on proven scams. The latest is a variation of the so-called "419 scam," named after the penal code that prohibits them in Nigeria.

We've all gotten the spam messages about a Nigerian prince promising rich rewards in exchange for a relatively small payment mailed to a mysterious overseas address. Now, 419 scammers have begun preying on businesses of all types -- including home medical equipment providers.

And instead of using the Internet, scammers are using TTY lines for the hearing impaired, which makes their calls untraceable.

"[One caller using a TTY line] wanted to purchase all of our blood pressure monitors," said Sandy Jones, owner of Austin Respiratory in Clearwater, Florida.

Jones sold the caller all the monitors she had, charged the caller's credit card for $600 and, after signing a $300 UPS bill, sent a large package overnight to Africa. She had sold equipment to immigrants before who sent products overseas, she said, so why should this be any different?

Shortly after, the bank that issued the credit card alerted Jones that she had been a victim of fraud and, because the criminal was at large overseas, her company would have to pay back the bank. According to authorities, the blood pressure monitors Jones sent are now most likely being sold on the Nigerian black market.

Extremely large orders, often for a vendor's entire stock of a particular product, should send up warning flags, authorities said, adding that the scammers frequently say they need the entire order shipped overnight, often to Nigeria.

Because of the international nature of the crime, it's unlikely law enforcement agencies will be able to help, so the answer lies in education of consumers and small businesses.