Some portable handsets have a static discharge protection circuit. When you walk across a carpet holding one, you may build up enough static electricity to cause the phone to turn off.

If this happens, turn the handset off for a few seconds, and then try it again. Low batteries can also cause the handset to stop working, though this is usually not sudden. Recharge the handset.

If that doesn't work, replace the batteries. Rechargeable batteries are usually located behind a removable door on the handset. Disconnect the batteries, take them to a consumer electronics store, and buy replacements.