The cell phone

911

• Call even if you have only one bar. A 911 call uses the network of any available carrier.
• Say where you are first: name of the park or trail, last known point, landmarks, GPS coordinates if you have them (your phone's maps or compass app shows them). Then what is happening, how many people, injuries.
• Don't hang up until the dispatcher tells you to. If the call drops, call back.
• Stay where you are after the call, unless told otherwise: your location has already been recorded.

Text message to 911

In many areas of the U.S. there is a text-to-911 service, but not everywhere. The rule is: "call if you can, text if you can't": if you can't speak (a deaf person or someone with a speech impairment, or speaking would put you in danger) or the call won't go through but a text might. Put the address or location and the type of emergency in the first message, in short sentences, with no abbreviations or emojis. The message may be delayed or not arrive, and the dispatch center doesn't receive your location as precisely as with a call. Check today whether your county has the service.

Saving battery

• Turn on low-power mode and lower the screen brightness to the minimum.
• Close apps; turn off Wi-Fi, Bluetooth, and background data.
• With no signal, the phone burns a lot of power searching for a network: turn on airplane mode and switch it off from time to time (for example, a few minutes at the top of every hour) to check messages or try to call.
• Prefer text messages over calls and data: they use less power and go through with a weak signal.
• Send your location to a contact (the maps app lets you share it) while you still have battery.
• In cold, keep the phone in an inside pocket: cold drains the battery. In heat, don't leave it in the sun.
• Always carry a charged power bank and its cable.