Final answer:
An addressable fire alarm system permits discrete identification of alarm signals at the detector level, using an ionization chamber and Americium-241 to detect the presence of smoke.
Step-by-step explanation:
A fire alarm system that permits discrete identification of alarm signals at the detector level is known as an addressable fire alarm system. This type of system uses detectors that have a unique address, allowing the central control panel to pinpoint exactly which detector has been activated in the event of a fire. The mechanism of a smoke detector is based on an ionization chamber, typically containing Americium-241, which emits alpha particles to ionize the air between two charged metal plates. This ionization process allows a current to pass between the plates. In the presence of smoke, the alpha particles are disrupted, decreasing the ionization and consequently reducing the current, thereby triggering the alarm.