Short Range Access Radio (Short Range Device)
A class of radio devices that communicate over a limited distance with low output power and are considered to have low interference potential. Industrial remote controls, gate and barrier controls, telemetry and alarm devices fall into this class; the conditions of use are defined per band.
The defining feature of the class is that the devices operate in a shared band and follow common rules. No frequency is allocated exclusively to anyone; everyone uses the same band, and what keeps order is the limits on power and transmission time.
- Power limit: set per band, based on the power radiated from the antenna.
- Transmission time limit: restricted by the duty cycle ratio.
- No protection against interference: these devices cannot claim protection against harmful interference; if there is another user in the same band, you have to live with it.
In a crane application this last item is very important. Intermittent operation of the remote control does not create a legal right; the solution is engineering. Move the receiver and antenna away from the inverter, the welding machine and the motor cable, place the antenna outside the panel in a vertical position, and leave at least about 20 cm between the control cable and the power cable. Safety, on the other hand, is based not on the radio but on hard-wired stop and limit circuits.
The context in which this term is used: Wireless Crane Remote Control Selection Guide