First, let me explain what a voice dialer is: This is basically exactly what it sounds like, instead of the dialer calling another computer to send signals, the dialer calls various (usually programmable) phone numbers to report alarms with a pre-recorded message (ie: "This is 123 My Street, Someone has broken into our home, please call the police.") Now, there are several problems with these types of dialers: 1. In most areas they are outlawed. Yes, this means that if you use one to call the Authorities (Police, Fire, 911, Hospital, etc.) then you will probably be fined, HEAVILY. The police do not like these things one bit. They will make sure you don't call them again. 2. In areas where they are not outlawed, they are usually ignored, why? See #3. 3. These dialers do not inform you of the problem at the premise, only that there is a problem. They do not tell you which sensor activated the alarm, only that you have an alarm. Police are not in a hurry to respond to this. If they get a call from a central monitoring station saying that your back door went off, they respond much quicker. 4. If they don't reach anyone at the pre-programmed numbers, then what? They tie up your line and keep calling. This can be a pain, and a hazard too. With central monitoring, you have one phone call, that takes 20-30 seconds and the dialer hangs up. 5. With the price of monitoring so low these days, these are pretty much outdated anyway. But some people refuse to pay $10-15 a month to have someone watch their home 24 hours a day/7days a week. So these are just some of the draw-backs to using voice dialers over central monitoring. If anyone out there uses a voice dialer, let us know. I would love to hear some more opinions on this type of hardware.

I am looking to install a Simon 3 system. I find most sensors/transmitters are available in "SAW" and/or "crystal" there is apparently a difference in technology. What is the difference? Why? Thanks Mark.