The real question, should be put forth, when employed how many should one expect to see, as interlocking fields, would be common sense. If each were capable of command and control of all the various weapons dedicated to the system, the only tactical maneuver may be to by-pass, unless you were able to get arty/air support. These wouldn't (as pictured)be a device employed at the company level, as all the weapons, the devices themselves, the remote command center etc. would require transportation and support, I'd assume a number of security personnel would also be attached to the set up. Those using this type of security will have made it hard to get in, but they've also made it hard to get out, the judicious use of mines in their egress routes may give them a bit of a surprise, along with the deployment of automatic AA devices to deny aerial supply- could also ruin their day. All this is based on, the 3.2 Miles, nothing says these devices couldn't be mounted on tracked vehicles/with weapons and used to secure movement areas, command resupply areas, etc. The Israli's are developing "bullet on bullet tech", first shot taken at robot, the coordinates of the weapon/flight path could be sent to correct weapon, and return fire could already be on the say, prior to the robot being hit-they can do that now. Drones A/C can do everything these stationary ground robots can do now (and more)
