... intercom doorbell, message recordable door phone, far remote distance,emergency call, also monitor kids & elder Operation :Outside room , Mount outdoor ... If no one answer the calling inside room ,outdoor unit will stop after 14 times of “Ding ... AA for outdoor unit , 3AA for indoor unitFrequency433.92MHzRemote distanceUp to 400metersbox size90x90x130mm new wireless doorbell,wireless intercom doorbell