A call to either one of these numbers can result in a high per-minute or per-call charge.
For example, a "psychic hotline" type of 1-900 number may charge .99 for the first minute and 99 cents for each additional minute.
Area Code 900 went into service January 1, 1971, but the first known to have been used in the United States for the "Ask President Carter" program in March 1977, for incoming calls to a nationwide talk radio broadcast featuring the newly elected President Jimmy Carter, hosted by anchorman Walter Cronkite.
One scheme involved inducing users to download a program known as a dialer that surreptitiously dialed a premium-rate number, accumulating charges on the user's phone bill without their knowledge.
Diplomatic services, such as the US Embassy in London or the UK Embassy in Washington, have also charged premium rates for calls from the general public.
In many European countries, for example France, Germany and the United Kingdom, it was common for organisations to operate customer service lines on premium-rate numbers using prefixes that fall outside the scope of the country's premium-rate number regulations.
In 1992, the Supreme Court allowed a law passed by Congress that created a block on all 900 numbers that provided adult content, except for those consumers who requested access to a specific number in writing.
The law killed the adult 900 number business, which moved over to 800 numbers, where billing had to be done by credit card.