Louroe Audio Monitoring AOP-SP-CF ceiling mount speakerphones designed to interface with various modes of audio/video transmission systems. They provide bi-directional audio with the receiving source (DVR, PC soundcard, IP Network cameras with audio, and video servers with audio). Both AOP-SP-CF and AOP-SP-CS contain a built-in electret condenser microphone and a 4 inch speaker. Also control potentiometers for adjusting the sensitivity of both transmitted and received audio. AOP-SP-CF is for Flush mounting to a ceiling. AOP-SP-CS is for Surface mounting to a ceiling