Simple old school supervised fire alarm circuit. Field circuit to the right of led's. Open the horizontal contacts to cause self restoring trouble (yellow for open ckt. fault) or close vertical contacts (could be heat detector) to create an alarm (red) requiring a "panel reset" done by opening contact on top left. Resistor at far right is referred to as an "end of line" or EOL, and is typically installed at the physical end of actual circuit in order to supply a controlled current returning to the trouble relay. This works on a parallel relay concept with coils requiring different voltages to operate. Sorry, a bit wordy but hopefully a decent representation of real world circuits worked before digital electronics and polling circuits. d...
PS: Having trouble using alarm operated relay as a latching relay because of the large difference in on and off voltage for relay coils within app. As it is, an open on the field wiring resets the alarm output as well. Not what should happen in a real alarm circuit.
PS: Lowered voltages and played with relay coil values as well as EOL value to correct previously mentioned problem. Now works as an actual real world alarm initiating circuit should.
