Vital-Sim Logic Simulator (VSLS)

A Boolean simulator that allows the user to build a track plan and then see and test the status of all the inputs/outputs, internal variables, timers, track circuit status and signal aspects at the same time. Nomenclatures appear adjacent to their respective icons.


After using the software supplied by the vendor of the solid state interlocking device to write and compile the device operating system program , the interpreter section of the Vital Signal Logic Simulator copies and reads the Boolean or Equivalent Circuits text file, strips out any unnecessary parts and rearranges the I/O bits and variables in alphabetical and numerical order. A user-friendly graphics utility allows the signal designer to draw the track and signal diagram using basic building blocks, then assign input and output bits to the various components.

Once the interface (circuit nomenclature) information has been established, the signal designer may use a mouse to select and toggle input bits. The actual Boolean logic program runs in the background and will display any changes to variable or output bits and also updates the track and signal graphic with such information as track occupancies and changes to signal aspects, switch positions, HD line circuits, code rates, etc. As individual bits are selected, the logic equations related to the bits are displayed at the top of the screen. If an improper response to a control function occurs, the erroneous Boolean equation is readily visible for immediate analysis and appropriate corrective action.

An additional feature of the basic VSLS package is the automatic, relay equivalent conversion graphic display of Boolean formulas. The display is active (permitting use of the mouse to change the status of relays shown) permitting visual review of all circuit activity. As test are made, active Boolean formulas are displayed and relay equivalents respond appropriately. Electric current flow on the appropriate path through contacts, to a particular relay coil, is indicated by a change in color of the connecting line (“wire”) and relay icon.