If the flashing mechanism in obstruction lighting circuits is installed so as to make it necessary for the lights to flash, the simultaneous flashing of all lights will be permissible.

[Statutory Authority: Chapter 47.68 RCW. WSR 96-17-018 (Order 164), recodified as § 468-240-150, filed 8/13/96, effective 9/13/96; O.M.&L. standards (part), filed 9/13/61.]