Pro Intercom MSM301 3-Circuit Master Station ModuleThe MSM301 attaches to an MS301 to double the number of available independent circuits from 3 to 6. The new circuits: D, E & F have all the capabilities of the original 3, including program audio insertion and control and the ability to use each circuit as either intercom or IFB with program muting or ducking. Connection of the two units is via D Sub connector and the short cable is supplied with the MSM301. As with the original 3 circuits, each of