Smoke and Carbon Monoxide detectors/alarms are extremely important for every home. People hate to spend the money on them, especially the higher quality (more expensive) detectors, and yet your very life can depend on them. There are many choices on the market today, ranging from cheap, basic models to extremely expensive, high-tech devices. There are two main types of smoke detectors: ionization detectors and photoelectric detectors. Most detectors utilize either one or the other of these technologies while some use both. Most detectors just use a beep-style audible alarm, while some talk, some have strobe lights, and some have a bright light to illuminate a dark area. Many detectors today are combining a smoke and carbon monoxide sensor, so you have dual protection in a single device. You can choose between AC and battery operated devices. Most (if not all) new homes are built with AC detectors in all of the vital areas, which usually contain a battery backup in case of a power outage. Many of these new detectors, installed in new homes, are linked together so that one detector will trigger all of them to sound their alarm. This is a very useful feature, since an alarm in the basement may not be heard by sleeping individuals in an upstairs bedroom. However, getting this protection in an existing, older home was almost impossible until a few years ago when manufacturers started utilizing wireless technology to allow communication between multiple detection devices. My wife and I recently decided to move our bedroom into the basement level of our home. It allowed our three children to all have a room of their own, but we were very concerned about what would happen if there was a fire and we did not hear an alarm go off on the upper level of our home. We were also concerned about the potential of carbon monoxide poisoning. It is the first time that we were not sleeping close to our children, as we were now down a level and on the complete opposite end of our home. We had a home security system installed, which also gave us some protection from fire, but we could not afford to have an adequate number of smoke and carbon monoxide sensors installed with it, as they were extremely expensive. Our security system is made by First Alert Pro, and when I explained my concerns about better protection, to the person installing the system, he recommended that we look into the OneLink combination smoke and CO alarms by First Alert. He told us that when one alarm goes off it sends a signal to every other OneLink detector in the house, causing all of the alarms to go off at the same time. He also told us that the alarms have a talking voice module, which actually tells you where the smoke or carbon monoxide is being detected. Research also shows that young children are more likely to wake up and take action when they hear a voice, rather than just hearing a beeping sound. I don't know much about that but I have read this information in several places on the Internet. I could not find the OneLink combination smoke and CO alarms at any local retailers, but I was able to find them at several sites on the Internet. Needless to say, they are not cheap! However, after researching this model online, I was impressed by the features and I read a lot of glowing reviews for them. Since you can add as many detectors as you want, whenever you want, I decided to start out with three of them and add more as I could afford them. The included instruction manual is pretty straightforward but setting up and installing the first detector was a little tricky. It's not that complicated but timing is a key element in programming this alarm. You start out by installing 2 AA batteries (included in the package), which will cause the alarm to say "Welcome, First Alert Smoke and Carbon Monoxide Alarm. No location programmed. To select location, press and hold test button now." This is where the timing part comes in. As instructed, you press and hold the test button until the Alarm starts speaking again, at which time you release the button again. When you do this, the voice module will say "To save location, press and hold test button after desired location is heard." The voice will then begin listing off room names in a typical house. The choices are as follows: Basement, Living Room, Family Room, Office, Kitchen, Dining Room, Hallway, Child's Bedroom, Master Bedroom, Guest Bedroom, Utility Room. Once you hear the name of the room that you want to setup the detector for, you must quickly press and hold the button down. It will announce the room name you have chosen and will tell you that the location has been saved. If you mess up this step, you can remove the batteries, wait for a couple of minutes and reinstall the batteries again, to start the entire process over. To add and link additional OneLink alarms, you must hold down the test button when you insert the batteries. Once you hear the unit chirp you release the button. At this point the green power LED should start to blink. You are then to hold down the test button on the first alarm you setup, until the second alarm chirps. You repeat these steps for each additional OneLink alarm you wish to integrate into your home. Once you have the main programming completed, mounting the devices is as easy as installing any other basic smoke detector, using the provided mounting screws. My wife and I started by purchasing and installing three of the First Alert OneLink Battery Operated Combination Smoke and Carbon Monoxide Alarms (SCO501NC-3ST). As all First Alert OneLink devices can be linked with each other, we will likely add a few smoke-only detectors in the near future. We have installed one of the OneLink detectors in the kitchen, one in the hallway (right outside our children's bedrooms), and one just outside our bedroom in the basement. So far they have been working flawlessly. We test them every couple of weeks or so, and pushing the test button on one detector causes them all to go off, as they are supposed to. The real test was when my wife recently had a "cooking accident," which caused a fair amount of smoke in the kitchen. The alarm in the kitchen went off first, which triggered the other two OneLink alarms in the house. I was in my office downstairs when the basement alarm sounded; saying "Warning, Evacuate, Smoke in Kitchen, Evacuate!" Shortly after I silenced the kitchen alarm, the hallway alarm went off, which set off the other two alarms as well. This time the spoken warning stated that smoke was detected in hallway. The alarms simply added to my wife's frustration in trying to get the burning dinner situation under control, but I was delighted that the alarms were working as promised. The First Alert OneLink Combination Smoke Alarm and Carbon Monoxide Detector allows you to build a safety network of wireless, interconnected alarms in your home. You can wirelessly connect up to 16 OneLink alarms in your home. When one alarm sounds they will all begin to sound. This device features a talking alarm, with an actual voice that speaks the type and location of the danger in your home. It is a 2-in-1 device, giving your home protection from both smoke and carbon monoxide. The smoke detector uses photo-electric technology, which helps prevent false alarms like those caused by cooking and shower steam. An EZ access battery drawer provides the ability to change the batteries without removing the alarm from the ceiling. The CO sensor is an electrochemical type, which is the most accurate technology available for detecting carbon monoxide. The OneLink produces a loud, 85db alarm, plus a talking alarm for added safety. The package includes the OneLink combination smoke and CO detector/alarm, a pair of AA batteries, mounting hardware and instruction manual. First Alert claims that this device has a 6-year lifecycle. The OneLink alarm will give a special chirping pattern, to let you know once the device has reached end of life. The dev