Beside your mountain climbing gear and training,
Make sure you have the following electronic equipment:

(1) GMRS/FRS 2 Way Walkie Talkie for communicating with the civilian rescue team, and keep some extra alkali batteries, and keep them warm in cold weather. Use channel 20 (462.675 MHz) if you are in trouble on the mountain.

(2) CB Walkie Talkie for communicating with the military search airplane, and use channel 9 (27.065 MHz) if you are in trouble on the mountain. Most military search and rescue aircraft have HF 2 way radios capable of communicating with CB radios, and ship and airplane radios that are carrying HF radios onboard.

(3) Global Position Satellite (GPS) Receiver for to know your exact location on the mountain, and keep those batteries warm in cold weather.

(4) A cell phone or a satellite phone with a portable generator source in order to keep the phone battery charged up, and keep them warm in cold weather.

(5) Flares or a light or radio beacon in order for the search aircraft to spot you.

(6) Don't just carry only a cell phone up the mountain with you, the battery may go dead, and then you would have no way to recharge that battery, and if you were in trouble on the mountain, and your cell phone is dead, you would have no way to make a distress call to the search and rescue team. Always carry back up 2 way radio communications equipment,.whether you are on the mountain for a few hours, or a few days, or a few weeks.

(7) If you or your climbing partners have trouble on the mountain, stay together, and do not separate. If you or your climbing partners do decide to separate, make sure you and your partners have functional 2 way communication radios in order to stay in touch with each other, or with the search and rescue team.

(8) Let somebody know that you have those communication equipment, and the 2 way radio channel or frequency that you are monitoring.

Those electronic equipment the I mentioned are widely available at any electronic store on or off the internet. Without those electronic equipment above, your chances of getting rescued from the mountain would be very slow, and your chances of survival would be slim if you are in a life threatening situation upon the mountain, and then you may end up being lost on the mountain, and never found. Always carry back up radio communication. When the climbers climb Mount Everest, they always have 2 way communication radios with them upon that mountain, and not just only their cell phone. So be safe, and not foolish and sorry.