The A1 (and probably other camcorders) allow you to set the shutter speed slower than the frame rate. How is this possible? For example, if I open the shutter for 1/6 of a second, 5 frames of video are captured while the shutter is open, therefore, each frame was not exposed for 1/6 of a second. It seems like the frame rate is as slow as the shutter could effectively operate.

Thanks for helping me understand this.

It's all electronic process. In your example, camera allows to accumulate images on sensors for 1/6 second just like photo cameras do, then closes electronic shutter and generates 5 identical frames based on accumulated image. The process is repeated 6 times per second resulting with 6 images sent out in stream of 30 frames.

Right, those slow shutter speeds are electronically created. There's nothing "mechanical" about them.