About 4 million people live in Maricopa County. Local officials say the 911 system gets overwhelmed if roughly 400 of them call at the same time.

The system has been overpowered twice in less than a year. The first was caused by a deluge of calls after a November 2015 earthquake, and the second was in June, when a meteorite exploded east of the Valley.

There are a limited number of people to answer calls during a crisis, said Michael Benjamin, a 911 technical manager at the city of Phoenix.

“For lack of a better way to put it, you have to have a butt in the seat,” Benjamin said. “You have to have someone available to answer that emergency call. As a taxpayer, I don’t think anybody wants to have hundreds of call takers sitting around overnight shift waiting for an earthquake or a meteor hit.”

A system that could handle simultaneous calls from roughly 1 percent of Maricopa County’s population — about 40,000 people — does not exist, Benjamin said.