Is the recorder offering you ten full hours of unattended recording capacity. When one side of the D-140 cassette is full, (5 hours of recording time) the Tel-Pro 10 automatically reverses to the other side of the tape, handing you a full ten hours of unattended recording time. Once both sides of the tape are filled up, the recorder then automatically shuts itself off! The Tel-Pro 10 turns on when the telephone headset is picked up and turns off when the telephone headset is placed back on hook so you'll obtain the ability of a full ten hours of unattended recording time of telephone conversation. There is no battery drain while phone is not in use.