What are they for? They look fairly large and expensive and all they appear to do is illuminate the word "Down". Surely if that's all they do they could just be replaced with cheaper LCD monitors displaying the word or something more descriptive. I know that modern ones are still large as they have just installed several at Bristol Parkway on the new platforms. I'm probably missing the blatantly obvious but i'm hoping that some one can answer this as I have been wondering for a while.
They are signal repeater indicators to advise the driver, train manager and platform dispatchers that the signal is off with the road set to the down line when the signal itself is obscured from the view of whoever needs to know. Same purpose as the ones at
BRI» which display the word OFF. Anyone care to elaborate further.