HP Poly Edge E Expansion Module for Edge E400 E500 IP PhonesThe Poly Edge E expansion module can help you reduce the number of lost customer calls, shorten transaction times, and support more accurate call routing. Super charge your Poly Edge E400 E500 series phones with 22 multifunctional line keys that can be easily set up as line registrations, call appearances, speed dials, direct stations or busy lamp field keys. Setup is a Plug and Play snap, with power and signalling provided by the host phone.