Is the backup unit necessary? How many should I use?

Yes, you need at least one backup unit in the alarm system, up to a maximum of 2 units per system + 2 auxiliary battery packs (one per backup unit). The number of backup units is defined according to the total consumption of the installed devices and the cable distances between the devices and the same backup units. Remember that between two backup units, you need at least 40 meters of BUS cable (with connected devices) and each unit must be combined with an 01801 power supply.