Oscilloscope Triggering

If you get two signals on the oscilloscope screen you have a problem with triggering. This video discusses ways to help with that problem.

[@funtechu]

The reason why you are getting what appears to be two stable phases when triggering is because the sine wave has a large amount of noise on it, so you are getting multiple rising trigger level crossings, including some on the falling edge of the overall waveform. To get rid of this, you can use holdoff as you show in this video, but an easier way that will usually work for cases like this is to enable "Noise Reject" which will add some additional hysteresis to the trigger, or to enable "HF Reject" which will add a low pass filter to the trigger path to clean up some of the high frequency noise components before triggering.