BSS stands for Bit Synchronous Single Wire. There are 2 different BSS signals. The difference between them is the ability to show different alternator errors: BSS-1 = only shows a mechanical or an electrical error BSS-2 = only shows a mechanical or an electrical error.
It is not possible to interchange BSS-1 and BSS-2 regulators with each other because the car ECU can ask about a certain error and if it doesn't get the right answer, it will show an alternator error (charging lamp on) on the dashboard.
The protocol consists of 7 registers where all the in-depth data is shown:
For example, on the BMW E60 series cars from 2003 and up there is a Valeo TG17C010 alternator mounted that has a BSS-2 system onboard. Some years later they used the same alternator, but its number is replaced by the TG17C048 which has a newer version BSS with different manufacturer and ID codes which is not interchangeable anymore and the software of the vehicle will require updating or error message deleting.