Review: DSC LC-171

Outdoor motion sensors make it easy to see if someone is on your property. With them, you can do things like turn on outside lights, record cameras, send emails, etc. Although this requires something like a home automation hub, security camera or alarm system, finding a reliable sensor can be very difficult. Frequent or late night false alarms can become a nuisance. Missed detection can be frustrating.

So I’m going to review the DSC LC-171. It was the 3rd sensor I bought to detect cars and people walking up my driveway and it will be the last one I ever use.


  • Dual Temperature compensated quad PIR sensor with sensitivity adjustment
  • 34.125 GHz Microwave with intensity selection
  • Dual tamper switches
  • Wired interface with NO & NC contacts
  • IP65 rated enclosure
  • Pet immunity lens included

Product Breakdown:
Internally, the connections are at the top, below that are the pair of PIR quad-sensors. The microwave module is in the lower section. The adjustments are on the right.  There is a tamper switch on the left. There are mechanical adjustments on the bottom and the middle.  


The sensors are both quad-PIR sensor, which is 4 sensors in a  single sensor package, but there are 2 of these so you get the benefit of having multiple sensors that have multiple points of view.

Externally, there is a rigid stainless steel mounting bracket which attaches to a wall. 

The PIR lens is multi faceted and comes with an internal, removable pet immunity lens mask. The housing is perimeter sealed with a rubber ring. 

The housing is sealed very well for outdoor use. Where the wire comes into the housing, there is a foam rubber block to seal the cable entrance.

Above the PIR is the LED lens. The RED LED indicates intrusion for walk test. There is also a buzzer for the same purpose.

You have the ability to disable the LED and BUZZER with a pair of dip switches.


The design of the unit is a mounting plate, the body and a cover.171d

Following the instructions, I mounted this about 4 ft above my driveway to detect vehicles and people walking by the sensor. I tied it into my alarm system as a monitor only zone and had it set to chime when it detected someone.

Installation for me was simple, I mounted it to my garage wall and ran the wires internally to the alarm and power supply.I used a 12V power supply, this device only draws 24mA (less than 1/2 watt).

Next I wired up the sensor. I used RED/BLK for 12V DC power and YEL/WHT for the sensor NC. Since my alarm system (Ademco/Honeywell 4219 Zone Expander) requires a 1 kΩ EOLR (end of line resistor), I put it inside the housing. I also wired up the TAMPER to the NC in series. I could have ran 2 more conductors and wired TAMPER to a separate zone, but I don’t feel like I need to dedicate a zone to tamper as the sensor will trigger if someone tries to approach it. If they do tamper with it, then the zone will not reset.

The EOLR is best placed in the housing and not in the alarm panel. By putting it in the housing, if the bad guys snip the wire, the alarm will know. There is a spare terminal block position to allow you to easily wire the EOLR. I didn’t use it since I jumpered the tamper and alarm NC outputs together using the resistor.


With all motion sensors, you play around with the settings over the course of days or weeks to get it where you want it.

Sensitivity is set by a 16 position rotary dip switch. The 16 positions are grouped into 3 distances, 7m, 10m & 12m. For each of these distances, there are 5 or 6 sensitivities you can adjust. The 5-6 discrete positions adjust from low risk to extremely noisy.


Physical adjustment

The unit has a mechanical adjustment for range between 3m and 18m. This will change the physical angle the PIR sensors are directed.


The sensor also has a mechanical adjustment to change its direction left to right. The unit covers about 90°, but you can adjust it between 0° and 180° by physically changing the angle.


I have a very challenging environment, the sensor looks across my driveway but beyond that is a grassy hill that gets lots of afternoon sun. When the wind picks up, the sensor goes nuts from the air thermals and the moving grass.

After testing settings, I eventually found that on the lowest setting for microwave and PIR, I was still getting too many false alarms.  The good thing was it was picking up my car as I drove by 100% .

After a few weeks of dialing it in, I was able to get it 100% detection with only one case of false alarms. The unit will false on my grassy hill on bright sunny days with fast moving cloud cover. I only get this one or two days a year, so not bad.

One complaint is the unit will trigger multiple times and sometimes it will keep triggering for many seconds after the intruder has passed. I have this hooked up to my alarm panel to chime, so it’s very annoying that it triggers more than once. My alarm panel has chimed every couple of seconds for up to 12 chimes. I fixed that by adding some smarts that only allows it to chime once by adding some hysteresis so it can’t chime again unless it stops chiming for 5 seconds.

I also have this sensor triggering recording on my camera system for the associated cameras. The cameras will record on any video motion, but once the LC-171 triggers, it sets an alarm event in Milestone. If the alarm is armed, then I get an email.

This unit appears to be made for DSC by the CROW Group, based on the


I’ve had this unit in use for over a year now. Of the 3 units I tested extensively, the LC-171 is by far the best for my situation.


It has the adjustments I need, the reliability not to miss anything and only false alarm one one or 2 days a year due to clouds. I can live with that. With the integration into my alarm panel and my Milestone security camera system, I am immediately notified whenever someone is coming to the house. When I’m home, the alarm panel chimes. When I’m away from home, I get an email with a photo from the camera.

This sensor gets a 5 out of 5.


4 thoughts on “Review: DSC LC-171

  1. is this good enough to detect somebody running across your property at night to reach our windows? Is there something better that you have since tested?

    great website by the way.


    1. Paul,

      This is still in use, I haven’t tested any other units as this one works really well. It will detect slow or fast moving people, it gets people cruising by on a bicycle, faster than I can run. If you are not worried about detecting vehicles, you can also consider the Risco Watchout to be very good also.


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