Which Alarm Do You Need? Seven Alarms, Seven Jobs

The alarm you need depends on the opening, not on which alarm is best: glass, or a door you want to hear being forced, wants a vibration alarm stuck to it; a door or window that should never open wants a magnetic entry alarm; a hotel or rental door wants a door stop or door knob alarm; the driveway wants a motion chime indoors; a shed or gate with no power wants a solar siren; and the walk to the car wants a personal alarm on your keys.

We sell all seven, and our best seller wins one of those jobs. The TremShield Vibration Alarm ($29.99) is a thin disc that sticks to glass or a door, sounds at 125 dB, and guards the one surface it's on. It loses on cost per opening, on travel, on the approach and on the walk to the car, so most rows below go to other products, several cheaper than it is.

Name the opening first: four questions

1. Is it glass? A bedroom window, a patio slider, a French door leaf, the pane in a back door. Glass is the one surface no lock protects.
2. Is it a door? A door you use all day wants something that ignores you coming and going. A door that should stay shut, or a door in a room you're only staying in for a few nights, wants something that sounds the moment it's tried.
3. Is it outside the walls? A driveway, a gate, a side path, a shed. Warning about the approach has to come from outside the house.
4. Is it you? If the worry travels with you, the answer clips to your keys.

Our alarm finder runs the same questions and points to a product in about a minute.

What sets each alarm off, and what each one costs

The seven alarms, one at a time

Vibration alarm, $29.99: glass and doors, before they give way

The vibration alarm reads movement in the surface it's bonded to and answers with a 125 dB siren. A pry or a strike moves the glass before it breaks, which makes this the one alarm here that reports an attempt rather than an opening. Press it onto a corner of the pane, the one nearest the latch. Fitting takes about a minute; give the adhesive a day to bond before you count on it.

One unit guards one pane or one door, so a room with three reachable windows needs three. It holds nothing shut. Inside a solid door near the lock it fires when the door takes a blow or a pry bar, and a hard knock can set it off too, so on the door everyone uses, switch it on only once the household is in for the night or out. The mechanism is covered in what a vibration sensor alarm is.

Entry alarm 4-pack, $19.99: the most openings for the money

The Door and Window Entry Alarm 4-Pack is four two-piece magnetic alarms. One half goes on the frame, the other on the door or window edge; when they part, the unit sounds at up to 125 dB. It doesn't care what the door is made of, and at about $5 an opening it's the row our best seller loses.

It reports an opening once it's open, never before, and it misses a pane broken while the sash stays shut. On a door you use daily it sounds every time someone comes home, so put them on openings that should stay shut: a basement hopper, a spare room window, the garage service door. The two types are compared side by side in vibration alarm or entry alarm.

Door stop alarm, $16.99: holds the door and sounds

The Door Stop Alarm puts a 120 dB siren inside a rubber wedge. Slide it under an inward-opening door and a push meets the wedge and the siren together, with a low, medium or high sensitivity setting. Nothing is installed. It runs on one 9V battery, sold separately, and the door needs about 0.75 inches of gap underneath, so measure first. It does nothing for a door that opens outward, and someone has to be inside to set it.

Door knob touch alarm, $19.99: hears the try

The Door Knob Touch Alarm hangs from the inside knob or lever by its cord and goes off at 120 dB as soon as a hand lands on the handle, so you hear the attempt with the door still closed. It fits where a wedge can't: a door with no gap underneath, or one that opens outward. It's a touch sensor, so a plastic, rubber-coated or painted-over handle may not register; test it on your door the day it arrives. Switch it off in the morning before you reach for the handle yourself. Both door alarms fit the carry-on security kit.

Wireless driveway alarm, $34.99: the approach

The Wireless Driveway Alarm is the only one that tells you before a person is at the house. Two weather-resistant sensors outside each pick up movement up to 24 ft away and reach the indoor chime from up to 400 ft, line of sight. Aim them across the path people walk, not down the drive, or passing traffic will trip them. The chime is indoors, so it helps the people at home, not a house left empty. Placement is in where to put the driveway sensor.

Solar motion siren, $35.99: where there's no outlet

The Solar Motion Siren + Strobe charges from a panel on top and hangs on two screws on a shed wall, fence post or the far side of a detached garage. When its motion sensor picks up a warm body crossing it, it answers with a 110 dB siren and a flashing red strobe right there. Four modes, including strobe only, for a spot near a neighbor's window. It can't tell a person from a deer, so point it along the walkway to the shed door rather than at the open yard. More in securing a shed without power.

Personal safety alarm, $14.99: on you

The Personal Safety Alarm is a pull-pin siren rated at 130 dB that clips to a keyring, a bag strap or a zipper pull. Pull the pin and it sounds until you push it back in. It's the only one that protects a person rather than an opening, and it needs your hand, so clip it where your hand lands.

One more, for completeness: the Disc Lock Alarm ($39.99) is a 110 dB alarm built into a disc brake lock, for a bike or motorcycle rather than the house.

Which two do most homes start with?

For most houses, the pair is entry alarms on the openings that should stay shut, plus vibration alarms on the panes a stranger could reach from the ground and the doors out of sight of the street. One reports an opening once it moves; the other reports force on glass or a door before anything opens.

Something cheaper comes before both. Driving 3-inch screws through the deadbolt strike and the hinges costs under ten dollars and changes whether a frame holds, which no siren does, as why doors get kicked in explains.

To count the vibration alarms, enter your reachable windows and doors here; it shows how many and the price for that number:

What none of the seven do

None of them contacts anybody. All seven are local noise that reaches the building and the street, with no monitoring center, no dispatch and no message to your phone. None of them is a lock, apart from the door stop alarm's wedge, and none records anything. If you need a text while you're out or footage afterwards, that's a connected camera or a monitored system, and we sell neither. What a siren that calls nobody still changes is laid out in what happens when a window alarm goes off.

Choosing between our alarms: short answers

How is a vibration alarm different from a door stop alarm?

A vibration alarm sticks to a pane of glass or a door and sounds when that surface is pried or struck, but holds nothing shut. A door stop alarm is a rubber wedge that slides under an inward-opening door and sounds at 120 dB while holding it.

Door stop alarm or door knob alarm for a hotel room?

A door stop alarm if the door opens inward and has about 0.75 inches of gap underneath, since it also holds the door. A door knob touch alarm if there's no gap under the door or it opens outward; it hangs on the inside handle and sounds when someone touches it, before the door moves, though a plastic or painted handle may not register.

Do I need a driveway alarm if I have window alarms?

They cover different ground. A window alarm fires when somebody is at the glass, while a driveway alarm chimes indoors when somebody crosses the drive, gate or path, up to 24 ft from the sensor, which is earlier. Skip it in an apartment, or where the only zone it can watch is a public sidewalk.

What is the cheapest way to alarm a whole house?

Magnetic entry alarms cover the most openings for the least money: the TremShield Entry Alarm 4-Pack is $19.99 for four, about $5 an opening. They sound once a door or window opens, and miss a pane broken while the sash stays shut.

Which alarm works for a shed or gate with no power?

A solar motion siren. It charges from its own panel, hangs on two screws, and sounds a 110 dB siren with a red strobe when someone walks across its sensor; aim it across the path, since it can't tell a person from a deer.

Pick the opening, then the alarm

Sort the openings that worry you into glass, doors, and the ground outside. Glass is the column with nothing on it yet, because every lock in the house is on something else. For glass and doors, one alarm is $29.99, two or three are $24.99 each, four or five are $19.99 each, and six or more are $16.50 each, so the 6-pack is $99.00 and saves $80.94 against six singles. Orders of two or more get the Home Security Guide by email; four or five add one free no-drill window lock, six or more add two. Free shipping to the US, Canada, the UK, Australia and New Zealand, with 30-day returns.