BOSCH Plena Voice Alarm Router is an expansion unit that may add six zones and 12 input contacts to the voice alarm system. It can use the integrated amplifier at the LBB 1990/00 voice alarm controller and offers inputs and outputs for one or two amplifiers in a multi- amplifier one or two-channel machine. It offers twin-channel operation for calls and BGM concurrently to a maximum of six special zones, the usage of plena amplifiers. Moreover, the single-channel operation is feasible with the simplest one-plena amplifier. A couple of routers also can share one amplifier, inclusive of the inner amplifier at the controller unit. It is possible to apply any variety of amplifiers from one up to the number of routers used. The controller helps with a/b wiring.