Not long ago homeowners who wanted to provide security for their property often had to lay out $1,000 or more to buy burgler-detection systems and have them professionally installed.
Today it's possible to buy inexpensive gadgets and systems that sound a loud alarm when someone attempts an unauthorized entry. And best of all, you can install them yourself -- even if your skills are limited.
The do-it-yourself devices include alarms that are simply hung on doorknobs, motion detectors that require no more installation than plugging them into an electrical outlet, and complete systems that can protect every room in the house. One door alarm costs about $10, while ultrasonic devices can cost less than $200.
Even the most complicated of these installations require the use of a screwdriver and drill, and the ability to string low-voltage wire between the system components.
Some of the devices, such as those that hang on doorknobs, can be used away from home in hotels and motels.
One of these is Regal Ware's Startler. About six inches long, it is hung from the inside knob of the door. When anyone touches the knob on the other side, the battery-powered device emits a loud, disturbing sound -- certainly obnoxious enough to drive off all but the most persistent intruder. Entry-Alert makes a similar device. Both sell for about $25.
Less expensive is Sunbeam's Stop Alarm. It's a doorstop that can be permanently or temporarily attached to the bottom of an entrance door. If the stop is moved a fraction of an inch, an ear-piercing, aerosol-powered whistle is triggered. Any further attempt to open the door is resisted by the wedging action of the stop. When not in use, the stop is flipped off. It sells for about $10.
Ultrasonic motion-detection devices, which look like small stereo speakers, bounce inaudible sound waves off walls and furniture. They are aimed in such a way as to create a zone an intruder must cross. The disruption of the sound waves trigger the alarm.
Master Lock Co. makes a motion detector called Ultrason-II. It's said to be capable of distinguishing between random room disturbances and actual intrusions. This may be important if you have pets that might trigger a less sensitive device.
A "satellite" horn can be plugged into the master lock unit so that the alarm sounds in another room. Or the satellite can be placed in a neighbor's house or apartment for monitoring while you're on vacation -- provided the electricity is coming off the same transformer as yours. Door and window detection switches can be added to the basic Ultrason-II unit, which sells for about $190. The satellite unit costs $45.
Radio Shack also sells an ultrasonic detector. Its regular price is $80, but it was recently on sale for $60. Knox Lumber Co. has a $125 ultrasonic system that, when triggered by an intruder, turns on house lights as well as sounds an alarm.
Systems that go beyond protecting just one door or room also are available in kits that come with detailed installation instructions. Master Lock's Crimefighter includes a master control two window or door sensor switches, connection wire and a manual "panic button" that will sound the siren even if the system has been turned off. It costs about $100 and is adaptable to step-by-step expansion.
"Hooking up the system is no more difficult than running (stereo) speaker wires," said a spokesman for Doyle Lock Co., Minneapolis wholesaler of Master Lock products.
A system sold by Radio Shack comes with seven components, including the control panel, alarm bell and window and door sensors. It sells for$80.
The do-it-yourself device systems may be purchased in hardware, catalog and electronics stores and from locksmiths.