The Nortel BCM Digital Station Module 32+ supports 32 digital telephones through one RJ-21 connector A DSM32(+) operating in single-density mode occupies two DS30 buses Set the double density switch to enable the DSM to carry 32 extensions over a single DS30 bus The Nortel BCM DSM32+ is compatible with the BCM 200/400 Main Unit, BCM 400 Expansion Unit, BCM 450 Main Unit, BCM 450 Expansion Unit and BCM 50 Expansion Unit