While testing my Bell BC-202 walkie-talkies I pressed the C button on unit 1 twice and unit 2 obligingly sounded the call tones. The problem is that unit 2 continues to sound the call tones every few seconds and I can't figure out how to stop it. I even switched both units off and took out the batteries. When I put the batteries back and switched them on again unit 2 went right back into sounding the tones every few seconds. It doesn't even care that I changed its channel. Any ideas?