ZM 2100 is the system main unit that includes a preamplifier with 6-zone selection (no internal amplifier). It allows to choose either a power-sharing configuration by using one or two external amplifiers (the second is needed to keep music in zones not paged) for all the 6 zones or to use an amplifier (or more) per each zone. As the amplified main unit, also ZM 2100 has input connectors for sources and can manage priority and route the two buses to the system zones.