roythebus
Now restoring MLL738, a former BEA airport coach. Follow its progress on FB Group Byeways Vintage Hi
Posts: 1,037
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Post by roythebus on Apr 2, 2018 9:44:19 GMT
Signals displaying a black aspect must be treated as signals displaying a red aspect.  |
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Post by bananaman on Apr 2, 2018 13:28:59 GMT
I would expect some amount of batteries involved to maintain the signals and a bit of distributed feeds. No? Seems like close to a single point of failure here. Modern systems usually have a UPS (Uninterruptible Power Supply) to maintain the supply if there's a power loss. That wouldn't have been practical back when the District was signalled though (1950s?) |
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Post by DistrictSOM on Apr 2, 2018 13:57:32 GMT
East end of the line 60’s west end of line mid to late 50’s
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Post by zbang on Apr 3, 2018 3:16:45 GMT
Modern systems usually have a UPS (Uninterruptible Power Supply) to maintain the supply if there's a power loss. That wouldn't have been practical back when the District was signalled though (1950s?) Even in the 1950s, battery stacks were common in railroad signaling systems. More likely that some bright-eyes thought the electric supply was reliable enough (ahem, cough) or they didn't like the cost of enough batteries and maintenance. Or... did they use AC track circuits at the mains frequency? Come to think of it, none of the books I have about UK signalling practice, not that I have many, mention backup power. is the District line signalling based on AC or DC circuits? (Which sends me at various web sites to find out.) |
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Post by principlesdesigner on Apr 3, 2018 3:50:07 GMT
The District line originally used AC track circuits, and in some areas still does, the frequency of these tracks was 33 1/3Hz. The signal relays, trainstop valves, points valves & detection etc. are also AC.
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