alt Hacker NewsElectric meters often blink a signal LED for every X kWh, so other devices can read the signal. I'm not sure if this is used for bidirectional communications, though.
Replies
NegativeLatency • last Tuesday at 5:30 AM
Smart meters have a whole protocol
No, but they also have a separate infrared interface for this.
https://en.wikipedia.org/wiki/IEC_62056