A system and method for determining on a continuous, real-time basis the proximity of the esophagus to an endocardial catheter during mapping, ablation or other endocardial catheter-based procedures, comprising an esophagus probe catheter and an endocardial catheter adapted for proximal signal transmission between each other. If the cradle is rocked without the baby, however, then the cradle only emits music but no baby sounds. The second-type impurity has an opposite polarity with respect to the first-type impurity. Attractive ornamental satiny green foliage is formed.