The audio spying listening devices are designed for the serious professional who needs the best in audio surveillance. We use a component called "Quartz Crystal" qhich stabilizes the frequency. All of these bugs can be supplied several fixed frequencies, in the UHF band. Each bug has a specific frequency, therefore using one of our multi channel receivers you can monitor audio conversations transmitted from multiple spy micro transmitters from a remote location. The transmitters are very easy to use. As soon as they are connected to a power surce, they begin transmitting all audio information within the room to the distant receiver. The audio clarity is unbelievable and there is no signal drifting as with low cost devices. The UHF frequencies ensure that only you will receive the information.