Without conscious intent and the synchronizing signal of short iterations it is hard to notice the difference between being on the path and off the path unless you stay on the path for a while.
Scientists have even engineered artificial switches to start glowing or giving off some kind of electrochemical or biochemical signal once they are switched "on."
科学家们甚至已经设计了人工开关，当它开启时能够发光和者发出电化学或生物化学信号。
3
He pressed the red alarm signal to see if it was on or off.