What are the critical factors to consider when selecting a communication method for a fire alarm system in a high-rise building with limited cellular signal?

When selecting a communication method for a fire alarm system in a high-rise building with limited cellular signal, several critical factors must be considered to ensure reliable alarm transmission. Firstly, signal strength and reliability are paramount. Since cellular signal is limited, alternative communication methods must be explored. A Digital Alarm Communicator Transmitter (DACT) utilizing a dedicated telephone line is a reliable option, but requires two independent phone lines per NFPA 72 to provide redundancy in case one line fails. Secondly, Internet Protocol (IP) communicators offer another viable solution by using the building's internet connection. However, the internet connection must be highly reliable and have a backup power source to ensure it remains operational during a power outage, as the fire alarm system’s reliance on the internet connection makes it a single point of failure if not appropriately backed up. Thirdly, a two-way radio frequency (RF) system, often involving a mesh network, can be implemented. These systems use multiple transceivers to create a robust communication path, bypassing the limitations of cellular signals within the building. The RF system must have sufficient signal strength and coverage throughout the entire building, tested and verified during installation. Fourthly, survivability of the communication pathway is crucial. The wiring or communication pathways must be protected from fire damage. For example, dedicated phone lines or network cabling should be installed in conduit or protected pathways to prevent them from being severed during a fire. Finally, monitoring and supervision are essential. The communication method must be continuously monitored for integrity. If the communication path is interrupted, a trouble signal should be immediately transmitted to the supervising station, alerting them to the problem. Selecting the appropriate method requires a thorough site survey, signal testing, and careful consideration of redundancy, reliability, and survivability to ensure the fire alarm system can effectively communicate alarms even with limited cellular signal.