(Portland, OR)  --  Portland police are warning the public about a telephone scam in which someone posing as an officer demands money.  The Police Bureau says callers claim to be police officers or sheriff's deputies and demand money to satisfy alleged outstanding fines, missed jury duty, or an arrest warrant.  Portland Police Sergeant Pete Simpson says the scammers typically instruct targets to buy reloadable cards and call back with the numbers.  Simpson says real law-enforcement officers never call people on the phone and demand they pay off fines or taxes or respond to warrants.