Conventional detectors are normally connected to the Fire Control Panel via dedicated circuits, each circuit protecting a designated 'Zone' or 'Area' of the building (the maximum size of which will often be governed by local standards). Detectors have two states, Normal and Alarm.
The Fire Control Panel will normally be arranged in a set number of Zones or Circuits, e.g. 1, 2, 4, 8 etc. and have 2 separate sounder circuits.