The 2GIG XCVR3-GC3 is a 900MHz transceiver and 345MHz receiver for the GC3 control panel. The GC3 is already equipped with a 345MHz receiver to speak with the 2GIG wireless transmitters like door contacts and motion detectors. This module physically replaces that receiver inside the GC3 panel. The XCVR3 adds the ability for the GC3 to communicate with 900MHz devices like the 2GIG-IMAGE3 image sensor. Without this module the panel is not capable of the required bi-directional signaling.