Isolation. Also is known as Lockout-Tagout. I hope this helps.
<span>A large organization minimum at-least 2 DNS servers are needed. DNS servers are each internet domain in need. and Multiple server farms distribute the DNS Server. One of the DNS Server is must in separate location. install DNS server on all domain controller. DNS server on every domain controller is must.</span>
Well think of it like this lets say this wasn't and security system and it was a video game console and remote.
Now the console or keypad or the main components the power on or shut off the devices and the remote or sensors are the secondary parts but they are needed to help the console or keypad figure out what they are doing.
You will type
400*2*1.5
1.5 is another way to say 1 1/2
