redundancy for track circuit

[onestrangeday]

thanks for the information provided. The reason I ask for this question is that one of the track circuit system I've seen does have two receivers and two transmitters for same track circuit. (transmitter works in hot standby--only one transmitter is working at the time, whereas receivers works in parallel, both receiving and comaring the track circuit level), in simple term everything has backup, it certainly costs much higher but reliability is enhanced.

Personally, I have not seen this kind of implementation in the past, it's also the reason I would like to ask has anyone seen this kind of design. But I can see it's not usual practice in UK.

Hi Peter:

ok, I see, so there is actual implementation on using 'duplicating' system for train detection purpose. I agree that it is very important for the logic of system to decided which one is normal (if other system is down) in order to determine the presence of train, otherwise WSF could occur. So have you seen any redundant design for track circuit ?

No. I am not sure that anyone has seen the need for the marginal reliability benefit vs the cost.

In aswering a question like this, you would need to think what failure modes would be avoided by the two receivers, and what failure modes will make both receivers show the track occupied. Would it really be worth it.

Peter