2.4GHz digital wireless transmission with a stable transmission signal. Two-way audio monitoring to speak to baby. High sensitivity, the crying voice is easy to be heard and the lamp will turn on to inform parents. Easy pairing, plug and play in. Position the transmitter at a distance of about 1.5-2.0 meters from the baby. Both parent unit and baby unit can be powered by DC 5V or 3*1.5V AAA battery.