The First Years 49 MHz Two Receiver Monitor provides peace of mind when parents are away from baby. The monitor set features 49 MHz technology, lightweight portability and sound lights that let parents see baby's activity level. For added convenience, they’ve included two receivers so parents can keep each receiver in a different room, or so two listeners can have a monitor handy at all times. Plus, low-battery indicator provides extra reassurance that when the monitor is quiet, it just means that baby is sleeping - not that the monitor isn't working.