Here are some tips to get the best out of the Sonim XP3 Sentinel phone:

1. For more stability, the keytone should be set to off. This can be done at Menu > Settings > Sounds > Key tone > Off 
   
   
2. For seamless operation when moving across cell boundaries, the GPRS should be set to always attached. Menu > Settings > Connectivity > Network settings > Attach GPRS > Always attached 
   
   
3. Please watch out for the GPS icon. If it is amber, the accuracy is poor. If it is green, the accuracy is OK. If it is red, it has not connected to the satellites. It may take more time to connect to the satellites if you are in non-ideal conditions like moving in a car or inside buildings. Always make sure that phone has maximum satellite view where ever possible, for .e.g.
   
   
   
   • Make sure the GPS icon is green before starting to drive
   • While in moving a car, always keep the phone on the dash board
   • Carry the phone always on the belt holster instead of keeping it in the pocket
   • Phone being in the vertical position gives better GPS performance
   
   
   
4. If you receive an incoming call from a non-ERC number after you've pressed the red-button, do not accept the call. In this case, after the LW icon on phone's screen has changed to alarm icon, the ERC call will start automatically after about 30 seconds. 
   
   
5. If you see "SS Error" or "Not allowed" when the phone is making call to ERC, don't worry. The ERC call is attempted after 30 seconds 
   
   
6. Always remove the phone from wall charger or USB connector when switching on or off the phone. 
   
   
7. Using WAP browser has shown some interactions issues with the LW functionality. Recommendation is to use Opera Mini to browse internet. Avoid browsing internet for longer durations. 
   
   
8. Java applications that use the Camera and Audio recorder are incompatible with reliable lone worker operation. Please do not use such applications.
   
   
9. When the phone is powered on, it will take about 10 to 15 seconds for the loneworker application to startup and be fully operational. Please wait for 15 seconds before placing any outgoing GSM calls. During this time, you can accept incoming GSM calls. In case, if you hear continuous beeps (E2E check failure on the screen) then power down the phone and restart the phone. 
   
   
10. The red button is active in the idle screen even when keypad is locked. It is not active in other screens. If any other screen is displayed, then press the "END" key twice and come to the phone's home screen before pressing the Red-Button.