Is it legal for an employer to listen in on conversations in the workplace

Is it legal for your employer to listen in or record private conversations in the work place. I feel that conversations that are had are being listened in on, without my consent. What are my rights and is it illegal to listen in when the employer is not at work. Conversations that are had are during work hours at the work place, but are private. Between myself and a co-worker. I work at a restaurant in the kitchen. We dont have an employee manual in place. I do know (through the grapevine) that we have surveilance cameras in place, but have recently found out that the cameras are not working. Hence, the recording device. I believe that the surveilance cameras that are at the work place have accessability through my employers smartphone. Since cameras are no longer working, I feel that they now can access audio through their smartphone. Almost as if, the video part of the camera is no longer working, but added audio to their non-working camera. If it's illegal, how do I stop it.