The Caroline Guitar Effect Pedals - Parabola Solid State Tremolo is a distinctive wave form modulation modeled after the Schaller TR-68. The sloshy, transistor-based sound gives you a beautiful effect without standing in the way of your playing. Similar to other Caroline Effects, the Havoc switch increases the speed and depth for some great expression already built in. AM is a classic, subtle amplitude modulation and the FM brings in a great frequency mod. Tough as nails construction with some serious style, it's this sort of attention to detail that we love from Caroline Effects.