Crisis is a broad term, and it can apply to too many scenarios. Despite that, the best response to pretty much every problem imaginable is to keep channels of communication open. The best channels will of course depend on the situation, so you want to investigate the integrity of all of them.

You need to have a clear picture of what can and will knock out your email, hard-line internet, cellular connections, cans with strings attached to them and anything else you use to stay in touch within your business and with your clients.