LONDONDERRY TOWNSHIP – Testing of Three Mile Island’s emergency warning sirens takes place around 12:15 p.m. today. This is one of two semi-annual tests. The system consists of 96 sirens located in parts of Cumberland, Dauphin, Lancaster, Lebanon, and York Counties within a 10-mile radius of TMI. The purpose of the sirens is to alert residents to tune to an Emergency Alert Broadcast Station for information from state officials. During tomorrow’s test, the Emergency Alert Broadcast System will not be activated.