Dual Stop Blokschema

Contacts at the station

Basic functions:

  • Pass to the computer 2 stops in the same block.
  • Operate 4 blocks with one pcb.
  • Reducing the number of required inputs S88.
  • Visual indication of active contacts.
  • The Open Collector outputs can switch up to 100mA to the ground.

How does it work..

At startup, the board is at rest, the output is open (= no contact).
We assume a normal train, where the oncoming locomotive makes contact to "Stop 1", then three actions happen:

  • an internal flip-flop toggles
  • a time-out timer start
  • the output goes "low" and the indication LED "on"

further incoming activities at "Stop 1" each reset the time-out timer. Once the locomotive reaches "Stop 2", next actions start:

  • a pulse is generated keeping the output low long enough for the program, the LED goes "off"
  • if the pulse expires, a second one is generated setting the output to ground, the LED goes back "on"
  • after the end of this pulse the flip-flop gets in its initial state, and the output is a representation of the condition at "Stop 1" and "Stop 2". Is either low, then the output will be low too.

for the program is the further state of the inputs of no interest, normal locomotive will halt at "Stop 2", and when the train leaves, multiple input pulses will alternate between high and low, always reset the time-out timer. Once the train passed the contacts, the time-out timer is reset and no longer expire, and resets the internal flip-flop should it be in a faulty state.