(MONEY Magazine) – Home-security systems are a good thing, right? Insurers think so: If you get a system that notifies an outside network, they'll knock 15% to 20% off your home insurance premiums. And this is a good time to buy. The average system costs $1,000 these days, down from $1,509 in 1990. But consider this: False alarms have become such a nuisance that the Los Angeles police department and others have decided not to respond unless a person confirms that there has been a break-in. Many burglars have gotten good at circumventing these systems--when they're on; 41% of victims didn't have the alarm on, according to a 2 1/2-year study conducted in the mid-'90s in Connecticut by Simon Hakim, an economics professor at Temple University. System or no system, there are things you should do now.

ALL DOORS THAT LEAD OUTSIDE SHOULD BE METAL OR SOLID-CORE (1 3/4-inch hardwood) and fitted with a deadbolt lock (minimum 1 1/2 inch).

SECURE SLIDING GLASS DOORS WITH BARS OR LOCKS or put a wooden dowel or broom handle in the door track.

MAKE SURE ALL POSSIBLE ENTRANCES ARE WELL LIT WITH A BULB THAT'S 40 WATTS OR HIGHER. Or consider buying motion-sensor outdoor lights--the automatic "on" function may scare a robber into believing he's been spotted.

--NELLIE HUANG