SINGCALL Wireless Calling System,360 Degree Waterproof One-button Pager (APE310) APE310: 01. Built-in silicone pad, 360 degree waterproof handling. 02. Small, thin, no screw, replace the battery easily. 03. Match to all of SINGCALL receiver. 04. Anti-temperature and humidity changes. Strong EMC anti-interference.