The RM-210F is an expansion unit dedicated for the RM-300X Desk top remote microphone. The number of zone selection keys and indicators of the RM-300X can be increased in 10 units per RM-210F.
From Remote Microphone
110 x 76.5 x 215 mm (W x H x D)
Extension cable x 1, linkage bracket A x 2, linkage bracket B x 2, screw for linkage bracket x 12