There were actually a series of generations of this, as indeed the competitor system from GEC-General Signal.
There are not n awful lot of them left now, the main era of the relay geographical interlocking being the late 1960s / 1970s; however they still exist, control some very important areas and will continue to do so I suppose for about the next ten years.
Their great advantage was that they enabled large MAS re-signallings to replace the previous mechanical lever frames quickly and enabled the use of less skilled design and site installation labour, maximising and factory production of standard units. The "sets"- in broad terms for a "signal", "point" or "track"- included all the relevant interlocking logic and site design involved connecting these together according to a schematic track layout; then, as if by magic, all the interlocking needed was there.
It was "plug and play" and "modular signalling" before its time.
In practice it was not quite as easy as that; in reality there had to be a variety of each sort of set and (because of the British desire for "site specific" in order to maximise functionality at any particular layout according to site peculiarities) there was then a need for significant "free-wiring" to add this different functionality- thus detracting from the advantages of the basic concept, although still meaning that the bulk of the basic interlocking had already been achieved by the logic built into the sets.
Disadvantage was that there were a lot of redundant relays as everything that might have been needed was built in, whether actually needed or not. Hence high first cost for relays not actually necessary and the pace to accommodate them all; also the ongoing cost of relay servicing, power consumed and of course the impact in unreliability.
Advantages included that likelihood of errors in the wiring minimised and since the sets themselves could be automated testing off site and the majority of site wiring was implemented by colour coded plugcouplered cables that just interconnected according to the track layout in theory it was very easy and testing on site could be minimised. Troube is that the genration of people who conceived, developed and were brought up on such systems are almost now gone and the systems need a lot of "getting into" so difficult for others to quickly pick up what they need to know and there are a fair number of "traps for the unwary" for those who aren't experts. Hence alterations on such systems always now undertaken with a degree of trepidation......
Hope that this gives an overview; I do have some specific info for various types but not in an easy format to share and also I am no expert myself.
If you have got some real work involving interfacing to a particular site you certainly need more expert detailed guidance than I am able to give. Indeed if any company has sub-contracted such work to a non-specialist designer then I'd say they were either ignorant or irresponsible.
(28-08-2013, 07:11 PM)kannati Wrote: Hello,
Can anyone give more guidance or material of Westpac Interlocking. I know this is GRI system for the control and interlocking of railway signalling functions. And also know that the relays are come with sets or units associated with specific signalling functions.
I would like to more details of this Interlocking working and interface with site.( I have seen this on networkrail standard 11201_B10 but I cant get more details of working and operation)
Thanks,
Kannati
