What is normal anyways? That’s a loaded question and one normally being asked to a psychiatrist, not an alarm installer. However with the terms, “Normally Open” and “Normally Closed” being thrown around with a lot of the products we carry we thought we’d d try and explain what it really means to be ‘normal’.
To start, picture a switch (show below). A switch can really only exist in two positions “open” or “closed” (Schrodinger and his ideas aside). Switches are the lifeblood of the alarm industry; a switch changing position is what tells alarm panels that things are “ok” or “not ok”.
So, how does this help explain what position is “normal”?
That’s the best part, for probably the only time in your life YOU get to dictate what “normal” is! A great example of this is a mechanical thermostat; we’ve all seen them where you simply slide the lever to your desired temperature. Inside the thermostat there’s a switch which is always OPEN as long as the temperature is ABOVE whatever you’ve set the thermostat to. As soon as the temperature drops below your setting that switch CLOSES and stays closed until the temperature goes back up above your setting. This is what tells your furnace to turn on and stay on to warm the place up, then turn it off again once it has hit your temperature!
So in this case, what is normal? Luckily thermostats and furnaces don’t use the term ‘normal’ as they really only have one function, BUT now imagine connecting that same thermostat to your alarm panel as a TEMPERATURE SENSOR to make sure your house doesn’t freeze. Your alarm panel will need to know what is ‘NORMAL’, so this is where it’s up to you! If you want your alarm panel to call you (meaning an alarm has been triggered) when the temperature drops BELOW what you’ve set the thermostat to you’d tell the panel that “Open” is normal, meaning everything is ok unless the thermostat closes. Vice versa if you wanted to make sure your house wasn’t getting to warm (and you’re going to get a massive bill from your heating company!). In that case you’d set the thermostat temperature to your limit and tell the alarm system that ‘Closed’ is normal, so the thermostat is always in the Closed position until the temperature goes ABOVE the setting you set the thermostat too than the thermostat will Open triggering an alarm with your system because it’s no longer NORMAL.
Who would have thought NORMAL could be so COMPLICATED?