The world already has many fully electronic communications networks that seek to match, buy and sell orders directly.

Thus individuals with brokers willing to match orders may be able to trade, while other individuals cannot.

On the New York exchange, trades are routed through a single so-called specialist, who matches buy orders and sell orders.

On Monday, there was no trading for the first two hours as an Amex specialist - the broker responsible for maintaining an orderly market - tried to match orders.

The market caller then matched orders on a price and time priority basis.

That could hurt electronic markets that simply match orders and have no market makers to provide liquidity in the market.

Those penalties came after investigators concluded that specialists had often stepped in to trade with investors when they could have matched public orders.

Instead of matching buy and sell orders, he in effect became purely a buyer.

The exchange said it was investigating whether a handful of specialists failed to match orders from small investors directly, making a profit instead by buying from one and selling to another.

The exchange's rules require that specialists directly match orders whenever possible.