Any sensor can start the other. They actually sound in the presence of smoke. They continue to sound until one of them is exposed to smoke. Ringtones stop about 30 seconds after the disappearance of the smoke. Disadvantages: these detectors are a little large (about 125 mm diameter and 50 mm thick). They each use three AA batteries and a 9V battery (6F22). But the interconnection consumes energy. They do not have a stop button, you must remove smoke to stop or pick up and move them. They and drop and can be easily fixed. The configuration for interconnection is pretty well explained. I followed the instructions step by step and managed the first shot. It has effective protection for a great price.
