Wireless meter and sensor bursts (868/915 MHz)
Data bursts from utility meters and sensors using two-tone digital signals.
What does it sound like?
Short, fast data chirps or buzzes.
Who uses it?
Electricity, gas and water meters, and industrial and home sensors.
Where and when can I hear it?
902-928 MHz in the Americas, 868 MHz in Europe.
The science
These devices use frequency-shift keying: instead of switching the carrier on and off, the transmitter hops between two nearby frequencies, one meaning 0 and the other 1, which sounds like a fast buzz or warble in a receiver. A meter's radio module encodes an ID number and the reading and sends a brief burst that a walk-by handheld, a drive-by vehicle or a fixed collector picks up. In Europe a common standard is Wireless M-Bus (EN 13757-4), which runs at 868, 433 or 169 MHz with data rates from 2.4 up to 100 kilobits per second depending on the mode.
Why use it?
Radio reading means nobody has to enter a yard or basement to read a gas, water or electric meter, and one module maker reports Wireless M-Bus batteries lasting 15 to 20 years in the field. In the Americas the 902-928 MHz band is designated internationally for industrial, scientific and medical use, and FCC rules let unlicensed devices there transmit up to 1 watt if they hop across at least 50 channels or use digital modulation at least 500 kHz wide.
Lore
The drive-by method is literal: a meter reader drives a vehicle down the street while an onboard receiver automatically collects the readings from meters along the way.
Easily confused with
- Wireless sensor bursts (433/315 MHz), from the same family
- LoRa (long-range chirps), from the same family