diff --git a/src/dsp/cmDspFx.c b/src/dsp/cmDspFx.c
index 67252a5..bbb1c68 100644
--- a/src/dsp/cmDspFx.c
+++ b/src/dsp/cmDspFx.c
@@ -2909,6 +2909,7 @@ typedef struct cmDspScalar_str
   cmDspInst_t          inst;
   _cmDspScalarOpFunc_t func;
   unsigned             inPortCnt;
+  bool                 allActiveFl;                  
 } cmDspScalarOp_t;
 
 cmDspRC_t _cmDspScalarOpFuncMult(cmDspCtx_t* ctx, cmDspInst_t* inst )
@@ -2966,6 +2967,7 @@ cmDspInst_t*  _cmDspScalarOpAlloc(cmDspCtx_t* ctx, cmDspClass_t* classPtr, unsig
   double             dfltVal[ inPortCnt ];
   unsigned           i;
   _cmDspScalarOpFunc_t fp = NULL;
+  bool allActiveFl = false;
 
   // validate the count of input ports
   if( inPortCnt == 0 )
@@ -2974,12 +2976,26 @@ cmDspInst_t*  _cmDspScalarOpAlloc(cmDspCtx_t* ctx, cmDspClass_t* classPtr, unsig
     goto errLabel;
   }
 
-  // locate the operation function
-  if( strcmp(opIdStr,"*") == 0 )
-    fp = _cmDspScalarOpFuncMult;
-  else
-    if( strcmp(opIdStr,"+") == 0 )
-      fp = _cmDspScalarOpFuncAdd;
+  if( opIdStr != NULL )
+  {
+    switch( opIdStr[0] )
+    {
+      case '*':
+        fp = _cmDspScalarOpFuncMult;
+        break;
+      case '+':
+        fp = _cmDspScalarOpFuncAdd;
+        break;      
+    }
+
+    // if the second character of the operator string is '$' then all input ports trigger an output
+    if( strlen( opIdStr ) > 0 && opIdStr[1]=='$' )
+      allActiveFl = true;
+    
+    
+  }
+  
+  
 
   // validate the operation function
   if( fp == NULL )
@@ -3012,7 +3028,7 @@ cmDspInst_t*  _cmDspScalarOpAlloc(cmDspCtx_t* ctx, cmDspClass_t* classPtr, unsig
 
   p->inPortCnt = inPortCnt;
   p->func      = fp;
-  
+  p->allActiveFl = allActiveFl;
   va_end(vl1);
 
   return &p->inst;
@@ -3039,7 +3055,7 @@ cmDspRC_t _cmDspScalarOpRecv(cmDspCtx_t* ctx, cmDspInst_t* inst, const cmDspEvt_
 
   if((rc = cmDspSetEvent(ctx,inst,evt)) == kOkDspRC )
   {
-    if( evt->dstVarId == kBaseOpdSoId )
+    if( evt->dstVarId == kBaseOpdSoId || p->allActiveFl )
       p->func(ctx,inst);
   }
 
diff --git a/src/dsp/cmDspPgm.c b/src/dsp/cmDspPgm.c
index 6725238..fb347bb 100644
--- a/src/dsp/cmDspPgm.c
+++ b/src/dsp/cmDspPgm.c
@@ -898,7 +898,7 @@ cmDspRC_t _cmDspSysPgm_UiTest(cmDspSysH_t h, void** userPtrPtr )
   cmDspInst_t* prp = cmDspSysAllocInst(h,"Printer", NULL,   1, ">" );
   cmDspInst_t* mtp = cmDspSysAllocInst(h,"Meter", "meter",  3, 0.0,  0.0, 4.0);
   cmDspInst_t* ctp = cmDspSysAllocInst(h,"Counter", NULL,   3, 0.0, 10.0, 1.0 );
-                     cmDspSysAllocInst(h,"Label",  "label1", 1, "label2");
+  cmDspInst_t* lbl = cmDspSysAllocInst(h,"Label",  "label1", 1, "label2");
   if((rc = cmDspSysLastRC(h)) != kOkDspRC )
     return rc;
 
@@ -924,6 +924,8 @@ cmDspRC_t _cmDspSysPgm_UiTest(cmDspSysH_t h, void** userPtrPtr )
   cmDspSysInstallCb(h, chb, "out", prp, "in", NULL );
   cmDspSysInstallCb(h, chb, "sym", prp, "in", NULL );
 
+  cmDspSysInstallCb(h, mdp, "val", lbl, "in", NULL );
+
   return rc;
 
 }
@@ -2055,8 +2057,8 @@ cmDspRC_t _cmDspSysPgm_ScalarOp( cmDspSysH_t h, void** userPtrPtr )
 {
   cmDspRC_t rc;
 
-  cmDspInst_t* add   = cmDspSysAllocInst(   h, "ScalarOp", NULL,  6, 2, "+", "in-0", 0.0, "in-1", 0.0 );
-  cmDspInst_t* mul0  = cmDspSysAllocInst(   h, "ScalarOp", NULL,  6, 2, "*", "in-0", 0.0, "in-1", 0.0 );
+  cmDspInst_t* add   = cmDspSysAllocInst(   h, "ScalarOp", NULL,  6, 2, "+",  "in-0", 0.0, "in-1", 0.0 );
+  cmDspInst_t* mul0  = cmDspSysAllocInst(   h, "ScalarOp", NULL,  6, 2, "*$", "in-0", 0.0, "in-1", 0.0 );
   cmDspInst_t* mul1  = cmDspSysAllocInst(   h, "ScalarOp", NULL,  6, 2, "*", "in-0", 0.0, "in-1", 0.0 );
   cmDspInst_t* in    = cmDspSysAllocScalar( h, "Input",      0.0, 10.0, 0.001, 0.0);
   cmDspInst_t* in_m  = cmDspSysAllocScalar( h, "Input_M",    0.0, 10.0, 0.001, 0.0);
@@ -2068,6 +2070,18 @@ cmDspRC_t _cmDspSysPgm_ScalarOp( cmDspSysH_t h, void** userPtrPtr )
   if((rc = cmDspSysLastRC(h)) != kOkDspRC )
     goto errLabel;
 
+  // Notice that changing 'in' or 'in_m' causes 'out' to be recomputed, but other
+  // changes are cached prior to 'add'.  This prevents the program from going into
+  // an infinite loop.
+  //
+  //     in   -> mult0
+  //     in_m -> mult0--+
+  // +-->fb   -> mult1  +----> add
+  // |   fb_m -> mult1-------> add --------+------> out
+  // |                                     |
+  // +-------------------------------------+
+  //
+  
   cmDspSysInstallCb( h, in,    "val", mul0, "in-0", NULL );
   cmDspSysInstallCb( h, in_m,  "val", mul0, "in-1", NULL );
   cmDspSysInstallCb( h, fb,    "val", mul1, "in-0", NULL );