Last year, while our company was building a large custom home,
someone got in over the weekend and stole tools from one of our
subs. We were lucky the thief didn't get any of our stuff
— we had ladders, staging, and some stationary shop
equipment unsecured in the house, and all the usual smaller
tools locked in a 14-foot trailer outside. We'd always done our
best to secure things by locking and chaining them as needed,
but there's really not much you can do to protect an unoccupied
After a second, similar theft, I looked into getting an alarm
system. There are plenty of products that will protect a
trailer, but I wanted one that would also protect equipment in
the building and around the site. DeWalt's Sitelock alarm
system (800/433-9258, www.dewalt.com) seemed to fit the bill, so
we decided to buy it.
We didn't know it at the time, but a very similar product is
available from Tattletale Portable Alarm Systems (888/835-5668,
We bought DeWalt's system almost a year ago; here's what we've
learned about it since then.
The Sitelock consists of a base unit and a variety of 900-MHz
wireless sensors. Components are sold separately, so you buy
only the ones you need.
Base unit. The base unit is the
"brain" of the system (see Figure 1). It uses 110-volt power
and contains a keypad, a siren, a strobe, a cellphone, and a
backup battery. When a remote sensor is tripped, a message
travels to the base unit, which activates the siren and strobe.
If you pay the monthly fee for a monitoring service, the base
unit also sends a signal to the monitoring station. The station
notifies whomever you tell them to — the police, you, or
The base unit can be used alone to
protect the area where it's installed or in conjunction with
wireless sensors at various locations around the site. If a
sensor is tripped, the base unit uses a built-in cellphone or
land-line backup to send an alarm signal to the monitoring
The base unit contains a motion sensor and an internal
vibration sensor to trip the alarm if someone tampers with the
unit or enters the area where it's installed. Although I put
the base unit in my cargo trailer, I could just as easily have
put it in the building.
The unit can be plugged in and placed on a shelf, or hung from
the wall with an optional lockable bracket. The system includes
stickers and signs to post around the site to indicate it's
protected by an alarm (Figure 2).
DeWalt provides stickers
and signs that can be placed around the site to warn thieves an
alarm is present.
Cable sensors. A cable sensor is
basically an electronic bike lock (Figure 3). On one end is a
black weatherproof box containing a transmitter and battery.
The other end plugs into the box and can be further secured by
adding a padlock. Once the system is activated, cutting or
unplugging the cable sends a signal to the base unit and trips
Figure 3.A cable sensor works like an electronic
bike lock (above). If someone cuts or unplugs the cable while
the system is armed, a signal travels to the base unit and the
alarm goes off. The loose end of the cable (right) plugs into
the locking device and can be secured with a padlock for added
security (far right).
We use cable sensors to secure ladders, scaffolding,
compressors, and any other stationary tools we can loop them
through. One of our cables malfunctioned after water got into
the box, and DeWalt replaced it free of charge. The cables come
in several lengths: 2, 6, 12, and 24 feet.
Container sensors. A container sensor is a
plastic box that contains a transmitter, a battery, and a
vibration sensor. You can attach it to objects like job boxes
and stationary power tools, with screws or built-in magnets
(Figure 4). Installing the sensor depresses a spring-loaded
button on the back; if someone removes an active sensor, the
button pops out and trips the alarm. The sensor also goes off
if someone moves the object it's attached to.
Figure 4.Container sensors are typically installed
on job boxes and stationary equipment. This sensor is
magnetically attached to the table saw; the alarm will go off
if someone removes it or tries to move the saw.
The sensor's sensitivity is adjustable. At the most sensitive
setting, the alarm won't go off if you walk by, but it will if
you brush against the object. I use the least sensitive
setting; it's less likely to cause false alarms but will still
go off if someone moves the tool.
Conventional security sensors. DeWalt
also sells an indoor motion sensor and a door/window contact
sensor (Figure 5). These sensors are much like the ones found
in a wireless home-security system. The motion sensor uses
passive infrared to detect moving heat sources — people
— up to 50 feet away. The door/window contacts mount on
individual doors and windows, and trigger an alarm when they
Figure 5.This wireless door/window contact is
being used to protect the door of a job-site trailer. Wireless
motion detectors similar to the ones used in home-security
systems are also available for use with the
Since we were mainly interested in protecting the trailer and
specific pieces of equipment, we didn't buy either of these
sensors. We could have used them to alarm the perimeter of the
buildings we work in, but chose not to because our customers
often stop by the site when we aren't there; we wouldn't want
them tripping the alarm.
Using the System
The Sitelock comes with a clear set of instructions and is
fairly easy to set up. It took me about an hour to program the
base unit and six sensors.
Remotes. The simplest way to arm and
disarm the system is by using a key-chain remote. Or if you
forget to bring the remote, you can use the keypad on the base
unit to punch in a security code.
The first time I tried the key-chain remote, it didn't work. I
called tech support and was told I wasn't pushing hard enough
on the button. I kept trying, and it still didn't work. In
frustration, I pushed so hard I was afraid I'd crushed the
thing, at which point it chirped to indicate the alarm was
armed. Eventually, the button loosened up and got easier to
One peculiarity I still find annoying is that the remote chirps
when you arm the system but not when you disarm it.
Monitoring service. The monitoring service costs
us about $30 per month. I suppose you could do without it, but
really, monitoring is the best part of the system. Each time
the alarm is tripped, I get a call from the service. The person
who calls asks for my password, tells me which sensor was
tripped, and asks if I would like the police to be sent.
During the time I've used this system, we've encountered a
number of problems — some that could be fixed and others
we've had to live with.
False alarms. We've had about eight
false alarms, and the cops have been out at least three times.
Most of the false alarms happened because someone with a
legitimate reason to be on site showed up when the alarm was on
and accidentally set it off. For example, a client came through
one weekend, saw a container sensor on the table saw, and
— wondering what it was — picked it up.
Actually, I'm not unhappy about the false alarms. Considering
how long we stay on the same site and how many people come and
go, there have been very few. Plus, having the police show up
helps prevent "inside jobs" — everyone on site sees that
the alarm system is working.
A couple of false alarms were caused by technical glitches
— once when the battery in the base unit was totally
discharged and another time when the base unit detected false
signals from the sensors.
I phoned tech support about the false signals, and the person I
spoke with diagnosed it as a problem with the base unit. To
DeWalt's credit, the company replaced the original base unit
with a newer model free of charge.
After that, there were no more false alarms from the
Battery backup. We've lost power to
the base unit a number of times, which is not a problem as long
as the power comes back before the battery is completely
But we did have trouble once when someone unplugged the power
over the weekend. The backup battery kept it going for a day,
but the system is designed to call the alarm service just
before the battery dies. I don't mind — I want to be
notified if the unit loses power.
The real problem came several days later. After the totally
dead battery was completely recharged, it sent in a false alarm
signal. I called tech support and was told it was a glitch in
the system. According to the manufacturer, this glitch does not
exist in the newer model we have now. I don't know for sure if
this is true, because the battery on our unit went completely
dead only that one time.
Sensor range. DeWalt claims that the base unit
can communicate with sensors up to 2,000 feet away. That may be
true for certain site conditions, but it was not the case for
us. I installed the base unit in an aluminum cargo trailer and
discovered that obstructions — especially metal walls
— seem to reduce its range significantly.
When the trailer was 60 feet away from the garage where the
stationary tools were, the system worked fine. But when the
trailer was parked 150 feet away on the other side of the
house, it was only about 75 percent reliable. Perhaps the range
would have been better if I'd put the base unit in the building
and a sensor on the outside of the trailer, but since the
trailer is mine I wanted to keep the base unit there.
DeWalt has plans to release a repeater for this unit later this
year. The repeater — designed to be mounted outdoors
somewhere on site — is supposed to boost the strength of
the signal between the sensors and base unit, making the system
more effective on large job sites.
Cell signal strength. My only major
complaint about the Sitelock is the weak cellphone in the base
unit. People working late on the job site have accidentally set
the alarm off, but the call didn't always reach the monitoring
center because the cell signal was too weak.
When DeWalt replaced our original base unit, we were told the
cell in the new one was twice as powerful as a handheld
cellphone. Maybe so, but I can't tell: I've stood in front of
the base unit talking on my cellphone while the unit's
indicator light says there is no signal.
I called tech services and was told the cell doesn't work well
in metal enclosures. If that's the case, the manufacturer ought
to produce an external antenna, because a lot of people will
want to put the base unit in a metal trailer or storage
Frankly, I doubt it was just the trailer; I experimented by
putting the base unit in the building, and the cell reception
wasn't much better there.
In fairness to DeWalt, the area where we were working is
extremely hilly and can have spotty cell reception. (On the
other hand, my own cellphone worked just fine.)
The current fix is to back up the cellular connection with a
land line. The base unit can be plugged into a regular phone
jack; if the alarm is tripped, it will try to call the
monitoring station by cell, but if that doesn't work it will
automatically switch to the land line.
The Bottom Line
In spite of its various shortcomings, I like this system,
mostly because it can secure an entire job site and notify the
police in the event of a break-in. We haven't had any more
thefts since we installed the Sitelock, and I feel more
confident leaving my tools on site with the system in
It isn't perfect, of course; certainly the cell reception could
be better and the sensor range more reliable. But given that
the system is portable and wireless, it is in general very
Moreover, on the occasions that we did have trouble with the
Sitelock, DeWalt was quick to replace broken or defective
components, and its tech-service advisers were excellent.
Kye Brewer owns Veritas Builders in Sonoma