Good day to all. I'm at the beginning stages of discussing a new project with a=20 customer and see that, right off the bat, I need to find some=20 off-the-shelf radio modules with the following characteristics: - multiple systems can exist in the same area without interacting - new transmitter modules can be added to a system at any time - it would be best if individual transmitters could be identified somehow - batteries last at least one year - work in heat and cold (+50 to -40 C) - withstand very high vibration - range of at least 100 feet when in close proximity to large metal=20 objects. The face of the enclosure is always exposed to open air but=20 that direction is pointing away from the receiver. - FCC *and* Industry Canada approval greatly desired - preferably in the 915 MHz ISM band, would consider other=20 frequencies. Prefer NOT to use 2.4GHz band. At this point, the individual modules are transmit-only but I might=20 consider bidirectional modules if going to a mesh-network was desirable. The modules will be going into a package about the size of a deck of=20 cards and I plan to have 2 or 3 "AA" cells for power. They will=20 transmit messages only while being added to the system or while a=20 fault condition exists. I *may* decide to add a periodic message of=20 some sort that says "I'm still here and working" but that is up in=20 the air right now. I'm planning to have unique IDs on each module with an easy way for=20 the receiver to learn each new module as it is added to the=20 system. Probably not more than 24 modules to any one system but=20 there will be multiple systems in close proximity to each other. I'm hoping someone can suggest small, inexpensive modules that are=20 readily available and reliable. Low cost is desirable. Many thanks! dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .