How 911 works
When you call 911 in the Washington suburbs, Verizon directs your call through several steps before it reaches an emergency response dispatcher. Here is how the system is supposed to work, and how it failed during the worst of at least 11 outages in Verizon's Virginia and Maryland call areas in the past two years. Read related article.
Sources: Verizon, Virginia State Corporation Commission. The Washington Post.