The DTM30 interlocks at Eastleigh used a spacial block in the approach road. We couldn't use the same approach at Clanfield, so we've tried the same approach as described in the DTM30 manual. That activates a route, preventing traincontroller activating others.
You need 3 elements on a switchboard to do this:
- A contact indicator that's activated by the DTM30 requesting the interlock. It's a general sensor whose number comes from the DTM30 front page.
- A point, that's set to THROWN when Traincontroller activates the interlock. The number is the same as programmed into the DTM30 interlock cell.
- A flagman, where all the logic is programmed.
The flagman's trigger is the contact indicator. When the contact indicator lights, the flagman will try to activate.
There is then a condition. The purpose of the condition is to say "don't let the the flagman activate if traincontroller is planning a train movement to or from Clanfield". We've used a block not reserved or occupied, and two routes not occupied:
Finally the operations make the flagman do something. When the flagman activates, we need to set the special point to THROWN to tell the control panel it has control. We also need to do something that prevents Traincontroller being able to drive trains in or out of the station. We've chosen to activate a route from the Clanfield critical block in the approach to platform 3. Effectively that blocks the tracks.
Finally when the flagman deactivates (ie when the contact indicator goes off in response to the DTM30 operator giving control back to the computer) we need to revers the last two steps - deactivating the route and setting the interlock point to CLOSED.
