For most customers at stores across the country, the standard shopping cart is nothing more than a receptacle to conveniently hold items while shopping. But for retailers, these carts, which can cost up to $200 each, are valuable and expensive to maintain (retrieval and repair of broken carts can cost retailers thousands of dollars each year).
To make matters worse, in an attempt to remedy the common problem of abandoned shopping carts on streets and sidewalks, some cities and counties have passed ordinances requiring retailers to contain their carts, often imposing fines on those that don’t comply.
All of this can make the lowly shopping cart a very expensive necessity. One solution is available from Gatekeeper Systems  of Irvine, Calif. The company has combined innovative proprietary technology with commonly available, off-the-shelf technology to create a system that keeps shopping carts where they belong — either in the store or in the parking lot, whichever the retailer chooses.
The system, called CartControl , includes a proprietary CentralTransmitter connected to an antenna that sends out a low-frequency 8-kilohertz digital signal. The antenna is buried in the ground near the perimeter of the store; the shopping carts themselves contain radios in the wheels that pick up the radio frequency signal if the cart gets too close to a designated threshold (called a wheel receiver).
If a signal is detected, the wheels automatically lock and can be unlocked only by an employee, explains Stephen Hannah, Gatekeeper Systems’ vice president of engineering.
The CentralTransmitter is typically located in the store’s warehouse or back-office area. It generates the digitally encoded 8Khz locking signal, which locks the CartControl wheel on the shopping carts when the wheels cross the buried antenna line.
The transmitter can protect more than 5,000 linear feet of perimeter boundary, a distance of almost one mile. The transmitter is also equipped with a General Packet Radio Service (GPRS) modem for mobile data service on 2G and 3G cellular networks. The GPRS modem communicates system status with a monitoring station located at Gatekeeper Systems’ headquarters.
To make sure the system runs continuously, even if the power is out, the transmitters are connected to an American Power Conversion BK-350 210-watt, 350-volt, six-outlet uninterruptible power supply (UPS).
“If the system were to go down for any reason — for example, if an antenna line broke because a landscape worker accidentally cut it, or AC power to the building is lost, or from damage because of a lightning strike — it’s important that we find out immediately,” Hannah says. “The UPS can keep the entire system running in the event of loss of AC power, but in the case of damage or tampering it is vital we find out quickly so we can keep the system running,” he adds.
The monitoring takes place in Gatekeeper Systems’ system monitoring center, collocated with its data center at its headquarters. The data center consists of about a dozen servers running Microsoft Windows Server 2008 , all housed in two fully enclosed APC cabinets, explains IT Manager Byron Tilman.
Some of the servers house the Microsoft SQL 2005–based database, which contains all of the data that Gatekeeper Systems collects from its customers and their cart activity. The servers are then backed up by three APC SmartUPS 3000 series UPSes.
The data monitoring system connects to the GPRS modems in each store’s transmitter, which monitors the CartControl system status in real time. If an antenna line is broken, for example, the GPRS modem sends a signal, similar to a cell phone signal, to the data center in Irvine, noting the time, date and cause of the alert.
When the perimeter system is compromised, CartControl’s SystemMonitor automatically generates an alert, which is sent via Simple Mail Transfer Protocol to the Microsoft Exchange Server to both its customers and field technicians. The alerts can be sent to a cell phone or e-mail account. Many of Gatekeeper Systems’ field technicians have e-mail set up on their RIM BlackBerry smartphones for just this purpose.
The combination of valuable intellectual property, proprietary technology and commercial technology has been important to the product’s success, Hannah says. In addition to keeping costs in line, the combination of these technologies has allowed the product to become more reliable, easier to maintain and easier to upgrade, he adds.
“We use off-the-shelf technology wherever it makes sense, and it’s proven to be a great way to increase system reliability and our responsiveness,” Hannah says. “We will continue to combine these technologies in the most effective ways for our customers over time.”