Fix minor startup frequency bug

toroid.html

@@ -1562,7 +1562,7 @@
                 };
                 
                 // Startup methods:
-                this.updateFrequencies(voltage_slider.value);
+                this.updateFrequencies(frequency_slider.value);
                 
                 this.chartCanvas = document.getElementById("chartCanvas");
                 this.chartCanvasContext = chartCanvas.getContext('2d');