I got a Sonoline B today from someone on Craigslist. Unfortunately it didn't have an owners manual. I was wondering what the button on the left does that changes the numbers from 1, 2 or 3. I did find the baby's heartbeat on my own. Yay! any tips or tricks would be nice too. Also, why is it a must to use aloe or a gel? I used lotion is that OK?