Attention please, it can't be used alone!!This is a wireless receiver only. Transmitter Bell is not included. Go to SINGCALL storefront to find all.(1-5,1-10,1-20 and so on) Purchase this item with some Transmitter Bells can build a simplest calling system. Bells: Go to SINGCALL storefront to find all one button pager and multi button pager. Search SINGCALL to find more. There are also many different combinations of wireless receivers and pagers in our store to meet your need. Where to install? Restaurant/Cafe/Fast Food Restaurant/Hotel/Golf Club/Bar/Night Club/Internet Cafe/Game Room/Karaoke/Hospital/Factory/Office/Anywhere needs attention of waiter. Have you ever been in a situation that you are ready to take your order in a restaurant but cannot find the waiter or waitress anywhere? The wireless attendant or server call paging system can solve your problem. Wireless fluid system is widely used in the service area. It includes the buttons for guests to use and the signal receiver for waiters to use. When the guest is in need, he or she just presses the button near him or her, his or her desk number will be displayed with music or vibration. Us Frequency Range: 433MHZ With Pager Quantity: 999PCS Specifications: 9.45*9.45*1.57 inches(240*240*40mm) Receiver Sensitivity: -108dbm Power Supply: AC220V/50HZ-12V/1A The Simultaneous Display Of Number: 1PC Letters Show: A.B.C.D.E.F.H.P(80 in English)