... ,penetrate cusion/room/desk,etc.factory good price offerReceivers can be sticked with adhesive sponge on TV Remote/Phone/Wallet/Calculator ... ,etc.Also can be hung with key ring.Penetrating Cusion/Wall/Desk/Room,etcSPECIFICATIONS ... controlled,not whistle/clap activated,strong anti-interference.Won't be triggered wrongly for drop or loud sound,power saved;•Easy ...