Product Overview The Serial Interface Module is a device to communicate with Convergence Network controlled lightbars. To minimize the number of discrete wires to the lightbar, control lead functions are wired to the Interface Module. The information is converted to a digital format and communicated to the lightbar via the serial communication cable. Lightbar patterns can be changed through the programming procedure. Control leads can also activate an Internal SignalMaster controller. If preferred, an external Federal Signal SignalMaster controller can link with the Interface Module and directly control SignalMaster operation.