Part 4 - An Introduction to Signaling
    
- Signal aspects 
- Basic signals 
- The ‘02’ signals 
- The ‘02’ caveat 
- The ‘01’ and the ‘03’ signals 
- Installing and testing signals 
- Signaling with diverging routes 
Part 5 - Working with signals
    
- Cornfield Meets 
- Dealing with AI issues 
- Working with signal blocks