SRD, Short Range Devices are radio devices that cover low distance. Based on its low power level is risk on inference is low too. Short range Devices to be operates under relaxed regimes of regulation, which called sometimes licence free. The power level is from 10 mW to 1W. The communication speed is from 100 bps to as high as 1 Mbps and more. A short range device can be a automatic meter reading device, a home automation system or anything else on low cover distance.
At ITU the term "unregulated frequencies" is not used. What is often meant by the term "unregulated frequencies" is the frequency bands for industrial, scientific and medical (ISM) applications.
The most commonly encountered ISM device is the home microwave oven operating at 2.45 GHz. However, in recent years these bands have also been shared with license-free error-tolerant communications applications such as wireless LANs and cordless phones in the 915 MHz, 2.450 GHz, and 5.800 GHz bands. Because unlicensed devices already are required to be tolerant of ISM emissions in these bands, unlicensed low power uses are generally able to operate in these bands without causing problems for ISM users. In the 2400 MHz band we will find Blue tooth, Wifi and ZigBee, but also SRD Short Range Devices with manufacturer specific protocols.