Worried that wily thieves could invade our home and steal items like the computer where this story got written and our aging Asimov's Science Fiction collection, we decided to get bids from residential home-security companies and learn how they'd protect our stuff -- and us.

We aren't alone in our worry about residential security: The security market is a $10 billion industry in the U.S., with a professionally installed and monitored security system in roughly 20% of homes, according to Bill Walker, senior vice president of research at First Research in Raleigh, N.C. Residential clients account for 40% of the industry, First Research reports.

Randall Enos

So just how would different security companies configure our Seattle home with a system, and what would they charge to alert the police about kicked-in doors, broken windows, or triggered motion sensors? To find out, we called ADT Security Services Inc., Brink's Home Security Inc., Monitronics International Inc. and Protection One Inc., all national companies that provide a free security review as part of their sales pitches.

Scheduling appointments by phone was straightforward. Once at our home, representatives spent anywhere from 30 to 60 minutes each assessing our house, outlining what equipment we'd need for adequate protection and writing a service bid.

Each of the recommended alarm systems included a programmable panel with communications technology to link our home to emergency dispatch centers, at least one motion sensor, door and window sensors, the option of "glass break" alarms for windows, a siren and a remote-control device with panic buttons. Smoke alarms can be linked to the systems to alert the local fire department of excess smoke or heat.

Our 1960s two-story home has a partial above-ground basement and garage topped off by a main floor upstairs. Representatives differed slightly in their depictions of how and where intruders tend to enter homes. (For example, one said they tend to enter via the front door and another said they tend to exit through it.) But they unanimously agreed that the basement, with a door facing the backyard and several ground-level windows, was our most vulnerable area. They all recommended at least one basement motion sensor plus window alarms (set off if the window is opened) or glass-break alarms (set off if the window is broken) downstairs, though they differed on the sensor's placement.

Reps from Brink's and Monitronics said that our garage door would be difficult to break in because of its front-of-house location and the particular garage-door-opener system we use. But the Protection One rep contradicted that, explaining that most garage-door openers work off remotes with low radio frequencies and can potentially be opened by determined thieves sampling different door remotes.

The ADT rep told us that if we keep a garage-door opener in a car parked on the street, we should always lock the car, as she knew instances in which robbers and attackers used garage-door remotes from unlocked cars parked on the street to gain entry into homes. All four representatives said we should arm the door from our basement den to the garage, just in case.

Upstairs, the reps all said that our windows were too high for a thief to seriously consider and wouldn't need window alarm or glass-break protection. But our two exterior doors would need alarms. They also said we'd need a motion sensor in the living room, though they differed slightly on where to place it.

All four companies offer systems that work over the home's existing phone lines, but each offers cellular backup for a slight charge. The representatives from ADT, Brink's and Protection One said that if a determined thief cut our phone line, then a system reliant solely on land lines would be unable to contact police, though sirens would still function. The Monitronics rep said he thought the alarm would go off if the land line were cut, but the other reps said this wouldn't happen because if that were the case, alarms would go off any time that inclement weather, construction, or repair work disengaged our phone line. Because of this issue with land lines, and because some homeowners use cellphones in lieu of getting land lines, all the reps recommended cellular backups for phone-line alarm systems.

Reps from ADT, Protection One and Brink's recommended GSM-only systems (using a cellular technology known as global system for mobile communications). Both ADT and Protection One offer GSM service, and Brink's will offer it later in 2008, the rep said. The Brink's rep encouraged us to get a radio-wave backup, which would transmit distress signals via radio waves to police or emergency workers, until GSM is available. ADT noted that VOIP-based systems (voice over Internet protocol) can be used as a backup or even as a primary alarm.

As for the cost, monthly monitoring prices ranged from $30.99 to $50.99, depending on whether we chose cell backup and a linked fire alarm, and whether we qualified for partner discounts. (ADT offered discounts to USAA and AAA members.) All companies required an initial three-year contract, payable monthly, after which shorter-term contracts were available. (ADT offers two-year contracts to USAA members.)

Installation prices varied, from $267.45 for Monitronics to $1,187 for ADT, without USAA discounts but including two linked smoke detectors. All four reps said we would need to pay an annual $10 alarm fee required by the city of Seattle to offset the costs of responding to false alarms, and every rep but the one from Monitronics said our price would include fees ranging from $50 for Protection One to $82 for Brink's to cover the permits for minor electrical work.

Of course, we're hoping that now that we've outlined our home's trouble spots and considered its lack of robber-attracting possessions -- just try hauling an old 300-pound TV out any door or window -- that this information alone will deter break-ins. But just in case, by the time this story prints, we'll be "armed."

Write to Jane Hodges at rjeditor@dowjones.com

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