Totally fascinating stuff ... Thanks for the explanation.
I'm curious though -- wouldn't the car on the track have created a sufficient conductor ? Or was it insufficient due to the rubber of the tires? C On 2/16/07, Bruce Metcalf <[EMAIL PROTECTED]> wrote:
Anil Kumar wrote: > Will someone please explain how this is done? I'll try, but read this with the understanding that my experience is with North American railroad systems, which may work a bit differently. Railway signal systems place low voltages across the rails (often 1.5 volts or less). When this is shunted by the presence of a train (or other conductor), relays detect this and set signals to display Stop indications. I once came upon an auto accident at a grade crossing and used the jumper cables from my car to short the rails and prevent additional carnage. As a result of the unexpected red signal, the next train approached the scene at a walking pace, rather than at speed. Sections of track are electrically isolated from one another with insulated joint bars. These are easily identified by the plastic color and size from conductive, metal joint bars. Normally, bypassing one of these insulators will only connect two adjacent blocks, and is unlikely to stop a train. OTOH, any place there is a switch or crossing, there are rails that cross from one side to the other and shunt the running rails if not insulated. If one of these gaps is bridged, then a Stop indication is likely. I'm a bit surprised to hear that a coin is sufficient, but then I haven't exactly tested this point. Questions? Bruce Metcalf, Lake Buena Vista, Florida
