TWO RECEIVERS: You can use the transmitter to control two receivers. Two receivers can be configured with different ringtones depending on your style and fun. WATERPROOF IP44: The transmitter is IP44 rated for perfect operation in rainy weather and is suitable for outdoor use. EASY TO INSTALL: just place the receiver in a power outlet. The blue LED flashes to indicate that the buzzer is working properly and is the perfect choice for people with hearing impairments. 36 DIFFERENT RING TONES: four adjustable volume, from 25 dB to 95 dB, for memory and tone selection. ENERGY-SAVING TRANSMITTER: The button can be fixed on the door frame with screws, or it can be fixed with double-sided tape or on the message.