Johnny, with newly upgraded memory, goes straight to the hotel room where he meets the client’s scientists. Before the data upload, he quickly installs a motion detector on the hotel suite door. This is a black box that he carries clipped to his belt. He uses his thumb to activate it as he takes hold and two glowing red status lights appear.
Once placed on the door, there is just one glowing light. We don’t see exactly how Johnny controls the device, but for something this simple just one touch button would be sufficient.
A little later, after the brain upload (discussed in the next post), the motion detector goes off when four heavily armed Yakuza arrive outside the door. The single light starts blinking, and there’s a high pitched beep similar to a smoke alarm, but quieter.
A sonic alarm is good, because it is omnidirectional. But being omnidirectional it might also notify the would-be attackers that they have been detected. Here the designers have erred too far on the side of caution. The alarm is so quiet that none of the scientists notice, and Johnny himself is lucky to be within a few metres when it goes off. The Yakuza burst in and slaughter the unaware scientists. It would almost certainly have been better for the alarm to be configured as loud as possible, ensuring everyone who needed to hear did so. And while the attackers would have been alerted, they might have been deterred by the thought of witnesses arriving.