The 4455 module is a fail-safe, bypass protection switch for critical ASI signals for broadcast or satellite applications. When a fault is detected in the primary input, and the secondary input is verified as good, the switch will activate, causing the secondary input to be switched to the module’s output. The 4455 includes a passive, fail-safe path that ensures there is an output even in the event of a total power failure. The health of an ASI signal is determined by monitoring digital clock lock, packet presence, and PID presence. The user can configure tests to define the minimum number of video packets and audio packets expected per second in a given service. The switch can operate in two modes: automatic or nonresetting. In fully automatic mode, the 4455 will automatically switch back to the primary signal once it’s been restored. In the nonresetting mode, the secondary input remains routed to the output, even after the primary input has recovered.