DU 31 is a two way wall speaker with flexible design suitable for paging and background music for several type of installations. It is equipped with a 3.5" woofer and a 1" tweeter. DU 31 includes a transformer for the connection to (100-70V) constant voltage lines. A power selector 8/4/2W at 100V and 25V (8W) soket make it possible to connect multiple speakers in parallel to a constant impedance line. Rear cover A1331 not included.