The specialist system used by the options exchanges is similar to the specialist system used by the equities exchanges described above. Under the options specialist system, specialists are required to make fair and orderly markets in the options classes assigned to them, maintain the limit order book in those classes, and maintain the exchange quotation in those classes. The options exchanges that use a specialist system have crowds at each specialist's post. A ROT is a member of the exchange who has received permission to trade in options for his own account. In return for trading privileges, ROTS have some affirmative market making duties, such as making a market upon request for the classes of options in which they are registered.
ROTS interact with the specialist to provide liquidity and depth.
Under the modified market maker system, all options on the same underlying stock trade in a centralized place on the exchange floor, which is also called a crowd. An OBO is an exchange official who administers the limit order book. The DPMs and LMMs are generally allocated by individual exchange rules a percentage of the executions in certain options classes traded by the crowd in exchange for performing duties similar to those of a specialist, including administering the limit order book. DPMs and LMMs are generally obligated to ensure that market quotations are accurate, honor guaranteed markets, and determine the formula for generating automatically updated market quotations. The crowds also contain market makers from different firms who trade for their own accounts.