digitsea 2 Plug-In 110v-220v Cordless Wireless Digital Doorbell Door Chimes & Bells with Battery 2.4Ghz Remote Control 100M Durable 38 Songs Polyphony Sounds 1. Please sue good quality,alkaline battery for the transmitter. 2. Don't install in sunny or rany place. 3.Keep away from metal to prevent any interference. 4.Please make sure the barcodes on their shells are the same,transmitter and receivers use the same codes to pair with each other. 5. Choose your favourate ring tone or long press the selection to change into loop mode.