AT&T Security Systems Frequently Asked Questions

What is the CRC Code For?
The CRC, or cyclical redundancy check, is in place to keep programmers from making typographical errors when activating a communicator. Learn more here!
Added:

Can I Change the Rev Chip on a Vista 21iP?
While you can upgrade the prom chip in a Vista-21iP, it may not always be advantageous to do so. Find out when you should, or shouldn’t upgrade the chip.
Added:

How Do I Enable the GSMVLP4G on my Honeywell L3000?
Once the GSMVLP4G has been physically installed, you must enable it in programming. Learn how to enable cellular alarm communication on the LynxPlus.
Added: