More lines - more power. Turn your Edge E Series phone into a powerful mediation console with the Poly Edge EM expansion module. Each expansion module offers three sides of 22 dedicated button representations - a total of 66 contacts/speed dials, right at your fingertips. Add up to two Poly Edge EM expansion modules to a Poly Edge E500/E550 phone. Add a Poly Edge EM expansion module to your Poly Edge E400/E450 phone.