Exchanges, brokers prepare for wild ride from Brexit vote

(Reuters) - Global financial exchange operators and brokers are preparing for volatile trading linked to Britain's referendum on Thursday on whether to stay in the European Union.

Markets have been racked for months by worries about what a Brexit, or a British exit from the EU, would mean for Europe's stability. The British pound rose to its highest level of 2016 after a poll showed that Britons had voted to stay in the EU.

If Britain left the EU, it would be the biggest blow to the 28-nation bloc since its foundation. The EU would be stripped of its second-biggest economy and one of its two main military powers, and could face calls for similar votes by anti-EU politicians in other countries.

Here are actions that some exchanges and brokers have taken in advance of the vote:

* CME Group Inc (CME.O) doubled the special pricefluctuation limits for all currency futures and options. Thecompany also reverted to the price fluctuation limits itnormally keeps during regular trading hours for allinterest-rate futures, allowing for bigger price swings than arenormally permitted during non-U.S. trading hours.

* CME "determined that there is a strong likelihood that the'Brexit' vote may result in increased price volatility in CME FXand CME and CBOT Interest Rate futures products," according to anotice. The company said "emergency action is being taken as aprecautionary measure and is intended to ensure fair and orderlytrading." * Intercontinental Exchange Inc (ICE.N) told customers thatcircuit breakers, known as interval price limit levels, for allICE Futures U.S. products are subject to intra-day changes basedon market conditions at any time.

* Nasdaq Inc (NDAQ.O) said it was closely following the voteand "will react accordingly to any market volatility." * Bats Global Markets Inc (BATS.Z), the second-largest U.S.equities market operator, said it "will be engaged in detailedmonitoring of all trading on the Bats markets, and the marketoverall." * CBOE Holdings Inc (CBOE.O), owner of the Chicago BoardOptions Exchange, said it had not put any special trading rules,restrictions or limits in place for the Brexit vote.

* At the close of business on June 21 futures broker R.J.O'Brien said it began charging customers 200 percent margins forgold, silver, the British pound and other contracts "in responseto expected volatility from the Brexit referendum." * Broker INTL FCStone Inc (INTL.O) also said it would chargecustomers 200 percent of the minimum margin set by CME forcleared futures for gold, silver, the British pound and eurocurrency. It was effective on June 16.

* Online currency broker FXCM (FXCM.N) on Wednesday raisedrequired margins for the second time in less than a month for 18major FX pairs, advising clients to put aside more funds againstpossible losses from the UK referendum.

(Reporting by Tom Polansek in Chicago. Additional reporting by Saqib Ahmed and Chuck Mikolajczak in New York.)