Digital linear heat detection cable with a 154°F (68°C) fixed activation temperature and a nylon outer sheath for UV protection and durability in outdoor or exposed locations. The cable is a twisted pair of low-resistance tri-metallic conductors insulated with a temperature-sensitive polymer; when any point reaches the activation temperature, the conductors make contact and signal an alarm. It connects to a conventional initiating circuit, or to an addressable loop through a zone or switch monitor module.