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diff --git a/src/main/java/com/jsyn/unitgen/SchmidtTrigger.java b/src/main/java/com/jsyn/unitgen/SchmidtTrigger.java
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+/*
+ * Copyright 2009 Phil Burk, Mobileer Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.jsyn.unitgen;
+
+import com.jsyn.ports.UnitInputPort;
+import com.jsyn.ports.UnitOutputPort;
+
+/**
+ * SchmidtTrigger unit.
+ * <P>
+ * Output logic level value with hysteresis. Transition high when input exceeds setLevel. Only go
+ * low when input is below resetLevel. This can be used to reject low level noise on the input
+ * signal. The default values for setLevel and resetLevel are both 0.0. Setting setLevel to 0.1 and
+ * resetLevel to -0.1 will give some hysteresis. The outputPulse is a single sample wide pulse set
+ * when the output transitions from low to high.
+ * 
+ * <PRE>
+ * if (output == 0.0)
+ *     output = (input &gt; setLevel) ? 1.0 : 0.0;
+ * else if (output &gt; 0.0)
+ *     output = (input &lt;= resetLevel) ? 0.0 : 1.0;
+ * else
+ *     output = previous_output;
+ * </PRE>
+ * 
+ * @author Phil Burk (C) 2009 Mobileer Inc
+ * @see Compare
+ */
+public class SchmidtTrigger extends UnitFilter {
+    public UnitInputPort setLevel;
+    public UnitInputPort resetLevel;
+    public UnitOutputPort outputPulse;
+
+    /* Define Unit Ports used by connect() and set(). */
+    public SchmidtTrigger() {
+        addPort(setLevel = new UnitInputPort("SetLevel"));
+        addPort(resetLevel = new UnitInputPort("ResetLevel"));
+        addPort(input = new UnitInputPort("Input"));
+        addPort(outputPulse = new UnitOutputPort("OutputPulse"));
+    }
+
+    @Override
+    public void generate(int start, int limit) {
+        double[] inPtr = input.getValues();
+        double[] pulsePtr = outputPulse.getValues();
+        double[] outPtr = output.getValues();
+        double[] setPtr = setLevel.getValues();
+        double[] resetPtr = resetLevel.getValues();
+
+        double outputValue = outPtr[0];
+        boolean state = (outputValue > UnitGenerator.FALSE);
+        for (int i = start; i < limit; i++) {
+            pulsePtr[i] = UnitGenerator.FALSE;
+            if (state) {
+                if (inPtr[i] <= resetPtr[i]) {
+                    state = false;
+                    outputValue = UnitGenerator.FALSE;
+                }
+            } else {
+                if (inPtr[i] > setPtr[i]) {
+                    state = true;
+                    outputValue = UnitGenerator.TRUE;
+                    pulsePtr[i] = UnitGenerator.TRUE; /* Single impulse. */
+                }
+            }
+            outPtr[i] = outputValue;
+        }
+    }
+}