Recent content by Signal Head

Luxury!

Derailment damage doesn't tend to produce the type of neat 'wavy' lateral displacement visible in the far distance on some of the images posted here and elsewhere, where the rails remain essentially at gauge and attached to the sleepers. There are two visible areas where rail fastenings have...

I used it in an email at work (rail industry) within the last year, then had to explain it to the recipient (older than me) who'd never heard of it.

Possibly the defect (buckle?) happened under the train you were on, so the front end passed through without incident and the driver was unaware of any issues? Happened at Tattenhall Junction (Chester) in 1971, buckle occured in the middle of a ten coach train at 70mph, causing two fatalities.

I have never known a 'greenfield' box where core functions were not supplied or backed by batteries. We (the region I worked most in) didn't typically backup semaphore electric lighting, and I have come across things like stencils fed from a 110v derived straight off the domestic supply with no...

But in that case it should have individual battery backup for critical items such as track circuits, colour-light signals and motor worked points. Along with battery backed supplies for lever locks (mechanical boxes) and control circuits, including blocks/bells. Another method is to use...

The Stockport area was due to be the first section controlled by the Ansaldo system. Despite beginning some of the PWay remodeling on the ground, and installing the interlocking equipment, various technical and operational issues combined to convince NR that it wasn't viable. The area that is...

Harrow & Wealdstone being probably the most (in)famous example. I vaguely recall some idea being bandied about which utilised a third inductor (this was well before TPWS). I cannot remember what it would have achieved or how it did it, seeing as you've only got two magnetic poles to play...

They wouldn't know until the rear of the 360 cleared the overlap at WH154, since the next track circuit was already occupied by the 810, so wouldn't 'see' the 360 entering it as well.

'Reverted' is the the term commonly used when a signal goes back to Red in front of a train, especially if owing to a (right-side) fault.

I agree that MAR was, and is still, provided when other forms are not appropriate. Perhaps I should have said that MAR (Main Aspect Approach Released from Red) was the predominant, or even the only, form of junction control for those schemes. In its original form it was an attempt to impose...

Flashing yellows are a means of conveying additional information to the driver, ie 'you are receiving cautionary aspects because a diverging route is set at the next junction", rather than because a signal is at red. They also remove the anticipation risk inherent in Approach Release from Red...

Yes, it is.

I cannot recall the document, or date, when it was, I think, effectively banned. I did manage to implement something similar a few years ago for very specific sighting reasons, but it was permitted only on the basis that the aspect would be unrestricted before the train reached the AWS, so the...

That suggests a 'two stage' approach release, which I am aware has been done in the past but is generally out of favour now. I wouldn't have expected it to have survived as a principle long enough to have been applied on the West Hampstead scheme, but it's possible I suppose. In the example I'm...