Ok, so I followed all instructions and got to the point of connecting the battery. The receiver sounded various tones as expected, but as soon as I turn on the transmitter, and operate the controls, I get a long continuos tone coming from the receiver. The tone would continue even if I turn off the transmitter. All controls operate as expected i.e. rudder, ailerons, throttle and elevator. What does the tone mean? I cannot find any references in the manual or this forum.