Communications
Cellular Failover
How automatic carrier failover keeps life-safety lines online during outages.
Cellular failover is the automatic switching of a cellular connection from one carrier to another when the primary carrier becomes unavailable. It is the mechanism that makes carrier diversity practical — the diversity exists so that failover has somewhere to go.
A dual-carrier cellular modem maintains awareness of both carriers. The primary carrier carries traffic under normal conditions. The modem continuously tests the primary connection. If the primary carrier fails (loses signal, drops the data session, or fails a health check), the modem brings up the secondary carrier and routes traffic over it — typically in seconds, with no human intervention.
For life-safety systems, the value of cellular failover is that an elevator phone, fire alarm panel, or emergency call box stays online during a carrier outage. Without failover, a single carrier outage could take an entire building's life-safety phones offline — an unacceptable risk and, in most jurisdictions, a code violation.
True911 supports automatic carrier failover as a core platform capability, with centralized monitoring that surfaces failover events so operations teams have visibility into when and why endpoints have switched carriers.
Frequently Asked Questions
What triggers a failover?
Failover is triggered by the primary carrier losing connectivity — signal loss, dropped data session, or failed health checks. The modem detects the failure and brings up the secondary carrier automatically.
How long does failover take?
Typically seconds. The exact duration depends on the modem, carrier provisioning, and whether the secondary carrier is kept warm (connected) or cold (must be brought up on failure).