The new WLM Wireless link module from Moore Industries provides wireless connectivity between remote field sites. WLM, a bi-directional, wireless module, employs frequency hopping spread spectrum technology and 32-bit CRC error correction for secure communications. The WLM supports either Ethernet or serial (RS-485) communications at speeds up to 188kbps and ranges up to 25mi, and operates at FCC license-free frequency ranges of 902-928MHz or 2.4-2.483GHz. For increased security, the WLM employs frequency hopping spread spectrum (FHSS) technology, where the transmitter changes the frequency at which it is broadcasting in a random pattern. Only a receiver programmed with the exact same algorithm is able to listen to and follow the message. For an intruder to successfully tune into a WLM system, he needs to know the frequencies used, the hopping sequence, the dwell time, and any included encryption. Given that for the 2.4GHz band the maximum dwell time is 400msec over 75 channels, it is almost impossible to detect and follow a FHSS signal if the receiver is not configured properly. Designed for use in field environments, the WLM operates in temperatures from -40 to 167F and humidity of 0-95%RH. It mounts on a DIN rail, supports Ethernet and RS-485 serial communications (including Modbus), and can be configured for a Master-Slave network, where one Master WLM can communicate with an unlimited number of “slave” WLMs. A WLM network can be used with remote data acquisition equipment, PCs, PLCs, RTUs and any process control devices equipped with a serial (RS-485), Ethernet or Modbus port.
