Each BSSC Expansion Chassis (WDR-EC) is provided by the WDR-MR and receives I and Q signals from the WDR-MR. A given unit can contain up to four high rate BSSC modules (20Mb/s to 17Mb/s total data rate). I data and clock, Q data and clock, combined data and bit rate clock signals from the locally or remotely selected BSSC module are provided on the rear panel. BSSC selection is controlled locally from the front panel and remotely through the WDR-MR. The selected BSSC lock indications are provided locally on the WDR-EC and remotely through the WDR-MR.