SALEM – A convicted sex offender who failed to register his residence and work address remains free on $500 cash bail, after pleading innocent.David Cox, 39, of 14 Foster St., Peabody, appeared Tuesday in Salem Superior Court answering not guilty to failing to register as a sex offender and failing to register his work address before Judge Howard J. Whitehead.The judge to set the same bail as previously established in district court and continued the case to May 12 for a pretrial conference.The charges claim that Cox, who had been homeless, failed to register as a sex offender in Lynn on June 23.Then he also failed to report his work place in Peabody to authorities on Sept. 20.Cox, a temporary laborer, was convicted of unnatural acts in September of 2003 out of Lynn District Court.Assistant District Attorney Jana DiNatale is prosecuting the case for the commonwealth.