At present, NASDAQ OMX PHLX, Inc. (the Exchange) Rules 1080(c)(ii)(C)(1) and (2) provide that an Order Entry Firm may not execute as principal against orders on the limit order book they represent as agent unless: (i) agency orders are first exposed on the limit order book for at least 3 seconds, (ii) the Order Entry Firm has been bidding or offering on the Exchange for at least 3 seconds prior to receiving an agency order that is executable against such order, or (iii) the Order Entry Firm proceeds in accordance with the crossing rules. In addition, Order Entry Firms must expose orders they represent as agent for at least 3 seconds before such orders may be automatically executed, in whole or in part, against orders solicited from member and non-member broker-dealers to transact with such orders. On November 10, the Exchange filed with the Securities and Exchange Commission a proposed rule change whereby the above exposure periods would be reduced to one second.The SEC is considering granting accelerated approval of the proposed rule change at the end of a 15-day comment period.  

http://www.sec.gov/rules/sro/phlx/2008/34-58949.pdf