The universal speaker unit can be used to install the 2 wires audio system in new or refurbished systems, where pushbutton panels of other manufacturers are present or required (mail boxes, patterned brass, compact sheet metal units, etc.), preset for a traditional speaker module (e.g. 2659N). The universal speaker unit has a contact base for the connection of 8 call keys; for systems with a higher number of keys up to 56 one or more key expansion modules must be used (1 every 8 keys)
