I am developing something identical to this system. it does have differences and additions but the base network and sensing devices are similar. how would i get a patent if mine is the same idea but different parts used and different way of building the system.
If your system is "identical" to this other patent then you would likely be out of luck. However, you noted that "it does have differences and additions." If these "differences and additions" make the system novel and non-obvious, then you may have a chance at obtaining a patent. You would need to have someone evaluate your invention, the other patent, and look for other prior art.
You may want to perform a patentability search to determine how different your system is from prior art already out there including 7,714,742. Try reaching out to a patent attorney or agent.