Radionics

Hi I am interested in working for a Alarm company. They mainly install Radionics systems. I was hoping somebbody can answer some questions and give me a basic idea how they operate. My first thing is what does the EOL resistor in a popit module used for? In general what is resistors used for in the first place? When you have say 25 popits on a popex module when one point is faulted how does the panel know which one it is? Does it talk to the panel and tell it's point number? I have read that say you have a point that has a bad popit and maybe it is point 20 who actually has the bad popit you may get alarms for other points. How can you determine that it is actually point 20 that has a bad popit? Do you just have to check each and every popit?