Investigation. Tim barber joins us with the questions being asked. Tim . Tim during those two hours, this is what you would hear [busy signal] busy signal, and now county officials want to know why. This is the sight and sound that you normally want to hear after calling 911. [sirens] two hours sunday and i, montgomery countys backup 911 system failed. During the time, fire rescue responded to two emergency calls. Tonight, the county executive launched an investigation into why the backup 911 system failed and if it played a role in the deaths of two people. Was the backup system tested before you ran it . It had been tested off and on, but it had not been used. The backup 911 system had been online for three weeks while the main system got upgrades. They believe that the backup system failed when an airconditioning system failed, which caused the system to shut down before it overheated. They need more redundancy than that. Tim during the failure, they urged residents to call 311 weat