Alerts
How you handle the output side of your security system depends on what you’re trying to accomplish. Systems have used a siren or a combination of sirens and remote monitoring for years; that remains a viable approach today. There may not be enough people near a home in a remote location to even hear a siren, though, so in this application you’ll need remote monitoring.
There are two basic ways to do remote monitoring — you can receive a notification when something needs attention or you can check in on the site periodically. Combinations of the two are perfectly reasonable, and there are many ways to do each:
Notification — The most common approach to remote monitoring is to send notifications to a person or site when the on-site system detects something of importance. For many years, nearly the only communications option was a direct modem-to-modem phone call to the monitoring point.Today, using the Internet, your options range from e-mail and instant messaging to VoIP telephony and custom client/server applications.
Polling — On-site processing and detection is required to generate notifications, but some conditions, such as nearby flooding or piling snow drifts, are simply very hard to detect automatically. Video cameras stationed around the property that you can access remotely through a broadband Internet connection let you look in whenever you choose; microphones let you hear any ambient sounds.
Combined polling and notification — One of the weaknesses of notification systems is that they can only tell you what condition they sensed, not the cause. Polling systems have a complementary weakness, in that with one you can readily determine what’s happening, but you can’t know when something is happening. The combination of the two — notification and polling — is very effective, because you can use the notification to connect in to the polling sensors and analyze the situation.
We’re only describing a notification system in this chapter; the TrackerPod chapter in PC Toys should give you everything you need to get started on the complementary polling system.