I think of a condo building as a building containing multiple units. It some areas if each unit has direct access to outside and there are proper fire walls a system for the building is not needed. “Town homes” are basically single unit houses connected together with fire walls between, so no system is needed. A condo building with interior common hallways usually will have a system, but sometimes the detector in the unit is a single station smoke alarm (or series of single station smoke alarms). The common area smoke detectors, waterflow switch, pull stations, etc. are connected to the building system with audible/visible notification devices in the common areas and sometimes audible notification devices in the unit. Sometimes the in-unit smoke is a system smoke with sounder base, it sounds right when it detects smoke but also sends a signal to the panel (which may or may not activate the building notification devices).