For eCall/ERA-GLONASS system, the reliability of the product must be guaranteed, and it can still work normally after strong collision. And when the automotive power supply can not work, support spare batteries.
The location of the installation needs to consider the structure of the vehicle, which will change after collision, and the wireless communication module needs to be highly sensitive. Smaller wireless modules are also more convenient for design.
At present, although there is a clear definition of specifications, some parts need to be changed later, so it can have the function of remote upgrade to reduce the later maintenance costs.