My previous topics have usually been about a specific signal or group of signals, but I 've decided now to start this one with the intention of it having a longer life. Where appropriate, I'll include links to older topics if they have relevent content.   I admit the idea comes from my "Following" Jon Fitness' topic which I find always interesting and very enlightening.   It's some time since I last posted - Signals for Horsted Keynes was the subject - 7mm as it happens.   Since then I've