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Archive: https://archive.today/mgQrI

From the post:

>Most smart home devices require power one way or another. You have to plug them in, recharge them, or replace their batteries at some point. Georgia Tech researchers think they have a better way with small metal tags that can signal when a door or drawer is opened, count reps in the gym, or even track bathroom use for elderly relatives. Their tags are battery-free, quiet, inherently private, and cost only a few cents each. They’re smaller than a penny. Like other kinds of smart home sensors, the tags are designed to be mounted on a cabinet or doorframe, for example, using a 3D-printed base. A small tab is attached to the corresponding door or drawer. When it’s opened, the tab strikes the metal disk, triggering a brief ultrasonic pulse imperceptible to human ears but detectable by a wearable device that logs the activity.

Archive: https://archive.today/mgQrI From the post: >>Most smart home devices require power one way or another. You have to plug them in, recharge them, or replace their batteries at some point. Georgia Tech researchers think they have a better way with small metal tags that can signal when a door or drawer is opened, count reps in the gym, or even track bathroom use for elderly relatives. Their tags are battery-free, quiet, inherently private, and cost only a few cents each. They’re smaller than a penny. Like other kinds of smart home sensors, the tags are designed to be mounted on a cabinet or doorframe, for example, using a 3D-printed base. A small tab is attached to the corresponding door or drawer. When it’s opened, the tab strikes the metal disk, triggering a brief ultrasonic pulse imperceptible to human ears but detectable by a wearable device that logs the activity.
[–] • 3 pts

the tab strikes the metal disk, triggering a brief ultrasonic pulse

So the remote control on a Zenith Space Command.

[–] • 1 pt

Zenith Space Command.

Hah, beat me to it. For those unfamiliar, the first TV remotes were mechanical, generating different ultrasonic frequencies when one of a few buttons was pressed.

I was also thinking of some apps that use this to communicate with microphones in stores to bypass privacy guards.

Or keyloggers that can tell keys based on the different sounds each key makes.

[–] • 1 pt

The remote for my ancient X10 system is ultrasonic, albeit electronically generated.