QUOTE: Originally posted by mvlandsw I have heard the detectors for two different tracks at the same location trying to talk at the same time. It gets confusing. If the report is not heard clearly the rules require a stop to inspect the entire train.
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QUOTE: Originally posted by Brak710101 I don't know if this was ever posted befor, but laws state that a detector must be placed every 40 miles, but most railroads place on every 20. So, if there is a problem with the transmission, or a broken detector, they can just wait till they pass the next detector (with out inspecting/stoping).
QUOTE: Originally posted by ChuckCobleigh QUOTE: Originally posted by mvlandsw I have heard the detectors for two different tracks at the same location trying to talk at the same time. It gets confusing. If the report is not heard clearly the rules require a stop to inspect the entire train. That doesn't have to happen. System design could include a receiver with each transmitter to detect when somebody else is talking. (Actually, receiver is not entirely accurate; only that part of what we call a receiver that detects the presence of an RF signal is really necessary.) If another carrier is on, the transmission is held off until the other carrier goes away. It's a pretty simple concept (called generally "carrier sense") and can also include something called collision detection as a part of an intelligent retry protocol. Even better is using one transmitter for the two closely adjacent defect detectors and eliminating the overlap condition, or at least routing a token line between the close detectors so that only one talks at a time. I'm kind of surprised that this particular situation hasn't been dealt with already, if in practice it does pose a problem.
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