The tattletale Base Unit is a completely self-contained unit. The heavy duty shell contains a PIR motion sensor, a cellular radio, an alarm panel, a siren/strobe and a backup battery - so even if the power and phone line are out the tattletale will send out an alarm! The tamper proof technology will trigger an instant alarm if the tattletale Base Unit is disturbed during an entry delay. An alarm event sends a data burst to a live 24/7 monitoring professional for fast action and response. The tattletale Base Unit can control up to 16 additional sensors on 8 programmable alarm zones. The tattletale base unit uses Cellemetry to provide a wireless data link to Tattletale dispatch so no phone line is needed!