The APOLLO-XPA-WB-14036-APO XPander Wireless Combined Sounder Base offers versatile installation options, allowing for wall or ceiling mounting. It utilizes a bi-directional monitored radio platform for reliable communication. With 32 selectable tones, including the distinctive Apollo tone, this sounder base ensures effective alerting. The built-in self-test feature, activated by a DIL Switch, sends a fault signal if the sounder fails to operate, ensuring consistent performance.