The Alpermann+Velte Rubidium SI module is an automatic switchover unit for IRIG -B signals. It analyzes and monitors two IRIG -B sources. If one IRIG -B source is lost, the IRIG -B output is automatically switched to the other error free source. Connected to a reference time source, the IRIG -B signal is monitored and compared to the reference time. The module offers a monitor function for errors in the IRIG -B, errors in the reference time source, for time differences between the two individual IRIG -B sources, and for the status information of all input sources.