第一次发文，恳请大家协助解答~
以下是BBC某篇新闻的节录，想知道的是"in which..."
这边的in是跟哪个字相关呢？
Crownstone is promoting a system in which a home's lights and
plug sockets automatically react to a resident's presence
based on them having a Bluetooth-broadcasting wearable or smartphone on them,
rather than waiting to be given a command.
感谢~