Tripcock Testers

I was able to explain how they worked, and we watched the "slightly whiter than violet" indicators go out. Every time though the associated signal was red; if a train fails to depress the ramp, can the signal still clear without some fancy jiggery-pokery (smashing glass, breaking seals etc...)?

So the whole safety of the trip-cock is based on the knowledge of one person?

If a train fails the tester the light will remain on but as soon as the replacing track circuit (next one) after the tripcock tester has dropped a alarm and indication should come on in the room controlling that area. Then the train is usually taken straight to the nearest depot to be checked. We usually only get called if two or more trains fail on the tester or if the same train passes on another tester

Ah but of course that is because no tripcocks are used on the Victoria line. Thus a train crossing onto the Picc must be proved to have its tripcock set. I suspect similar arrangements were in place at Ealing Broadway for trains crossing to the District though I don't know.

Oddly enough, that wasn't the case! EAB2056 could clear onto the District even without the tripcock detected. If we had decided to retain the link that would have been almost certainly altered to match the Finsbury Park arrangement.

Yep and changed quite frequently as a result, I changed those at Acton Town quite a few times, especially the one on the WB local. I changed both at Wood Green, the one on the EB being most troublesome as I recall.

With regard to being interlocked with the signalling system the function of the tripcock tester is not interlocked, however, the tester itself is interlocked in order to prevent back tripping of trains performing reverse direction movements. Thus there are two basic types of tripcock tester, those with and those without motors. Those with motors are required to pull down the ramp when reverse direction movements are cleared over them such as movements into and out of the sidings at Acton. My recollection is that all four tripcock testers at Acton have motors whereas only the WB one at Wood Green has a motor, there being no move from the siding to the EB.
Thus the signalling lowers tripcock ramps just as it does trainstop arms as required when clearing reverse routes over them. I don't think anyone asked the question but there is the answer !