| 摘要 |
<p>An alarm device is provided for detecting blockages in sewer pipes that connect structures to sewer lines. A clean out cap has a microphone positioned to detect ambient sound in the sewer line, and send a signal indicative of the level of sound to an alarm device. The alarm device has means to indicate an alarm condition if the level of ambient sound in the sewer detected by the microphone falls below a predetermined level.</p> |
