Firmware
The SL42, SL45 and SL45i share the same electronic components, and thus firmware can be exchanged between them. It can enhance functionality of SL42 and SL45 with Java support. Relatively simple structure of the firmware code, and the ease of new firmware installation (standard serial cable included in the box is suitable) led to many custom firmware modifications (patches) sprung over the Internet. These correct software bugs, change the phone's graphics, or even add new functionality like key remapping, calling pictures, or detailed battery information.
Read more about this topic: Siemens SL45