Internal lock and external lock for point machines

[Peter]

Thanks Peter

My work needs to test function of point machines but I could not understand clearly for internal lock and external lock. However, I found out that internal lock is usually required in Depot area and external lock is often required in mainline..please correct me if I am wrong. Most of the time mainline requires non-trailable points and depot is allowed for trailable points. Am I right?

Below I have a picture for external lock. Please help confirm my thought.

Thanks
Arnut

The sort (and hence the position) of the log is not really dependent on where it is used, it is more a function of the type of machine that a particular railway authority tends to use. In the UK, the majority point machines have internal FPL, whether on main lines or elsewhere.

The matter of trailable point is again a matter of railway authority practice. In the UK, because we have stretcher bars throughout the points, the are not trailable. The only place where one would have trailable points in the UK would be where there are hand points (which would typically be in depot areas, but motor worked points would not be trailable.)

The picture that you posted is of a point mechanism with which I am not familiar, but it looks as though the item you have circled is some sort of lock associated with the switch rail on that side. In the sense that this lock is not inside the machine, I suppose it would be classed as an external lock, but I cannot say with certainty because I do not know its function.

Peter