diff --git a/audio.h b/audio.h
index d3ff33a..f75be06 100644
--- a/audio.h
+++ b/audio.h
@@ -5,6 +5,8 @@
 #ifndef __iop_audio_h__
 #define __iop_audio_h__
 
+#include "config.h"
+
 enum RxInput {
   RX_RIG_IN = 0,
   RX_USB_IN,
@@ -31,6 +33,7 @@ void audioInit();
 void audioSelectTxInput(TxInput);
 void audioTransmit();
 void audioReceive();
+void audioCalibrate(IOPConfig *, char, char, char, float, bool);
 
 #endif
 
diff --git a/audio.ino b/audio.ino
index 8ba3466..5c51e1d 100644
--- a/audio.ino
+++ b/audio.ino
@@ -230,6 +230,21 @@ void audioTransmit()
       // Now switch to the mic input, and set the mic gain.
       audioCtrl.inputSelect(AUDIO_INPUT_MIC);
       updateTxMicIn();
+#if defined(FACTORY_CALIBRATION)
+      USBSERIAL.println("==============================");
+      USBSERIAL.println("Transmitting with Mic input");
+      USBSERIAL.print("Mic gain: ");
+      USBSERIAL.println(iopConfig.txMicInGain);
+      USBSERIAL.print("Mic volume: ");
+      USBSERIAL.println(iopConfig.txMicInVol);
+      USBSERIAL.print("Mic calibration: ");
+      USBSERIAL.println(iopConfig.txMicInCal);
+      USBSERIAL.print("TX audio level: ");
+      USBSERIAL.println(iopConfig.txRigOutLevel);
+      USBSERIAL.print("TX audio calibration: ");
+      USBSERIAL.println(iopConfig.txRigOutCal);      
+      USBSERIAL.println("==============================");
+#endif
     }
 
     // Allow both transmit and receive audio output channels.  This is safe
@@ -269,6 +284,260 @@ void audioReceive()
   }
 }
 
+//======================================================================
+
+void audioCalibrate(IOPConfig* c, char cmd, char subcmd, char parm, float value, bool set_value=true)
+{
+  switch(cmd) {
+    case 'r':
+    case 'R':
+    // RX audio parameters
+    switch(subcmd) {
+      case 'r':
+      case 'R':
+      // Rig input
+      switch(parm) {
+        case 'l':
+        case 'L':
+        // level
+        if (set_value) {
+          c->rxRigInLevel = int(value);
+          updateRxRigIn();
+        }
+        USBSERIAL.print("rxRigInLevel: ");
+        USBSERIAL.println(c->rxRigInLevel);
+        break;
+
+        case 'v':
+        case 'V':
+        // volume
+        if (set_value) {
+          c->rxRigInVol = value;
+          updateRxRigIn();
+        }
+        USBSERIAL.print("rxRigInVol: ");
+        USBSERIAL.println(c->rxRigInVol);
+        break;
+
+        case 'c':
+        case 'C':
+        // calibration
+        if (set_value) {
+          c->rxRigInCal = value;
+          updateRxRigIn();
+        }
+        USBSERIAL.print("rxRigInCal: ");
+        USBSERIAL.println(c->rxRigInCal);
+        break;
+      }
+      break;
+
+      case 's':
+      case 'S':
+      // Speaker output
+      switch(parm) {
+        case 'c':
+        case 'C':
+        // calibration
+        if (set_value) {
+          c->rxSpkrOutCal = value;
+          updateRxSpkrOut();
+        }
+        USBSERIAL.print("rxSpkrOutCal: ");
+        USBSERIAL.println(c->rxSpkrOutCal);
+        break;
+      }
+      break;
+
+      case 'l':
+      case 'L':
+      // Line output
+      switch(parm) {
+        case 'l':
+        case 'L':
+        // level
+        if (set_value) {
+          c->rxLineOutLevel = int(value);
+          updateRxLineOut();
+        }
+        USBSERIAL.print("rxLineOutLevel: ");
+        USBSERIAL.println(c->rxLineOutLevel);
+        break;
+
+        case 'c':
+        case 'C':
+        // calibration
+        if (set_value) {
+          c->rxLineOutCal = value;
+          updateRxLineOut();
+        }
+        USBSERIAL.print("rxLineOutCal: ");
+        USBSERIAL.println(c->rxLineOutCal);
+        break;
+      }
+      break;
+
+      case 'u':
+      case 'U':
+      // USB output
+      switch(parm) {
+        case 'c':
+        case 'C':
+        // calibration
+        if (set_value) {
+          c->rxUSBOutCal = value;
+          updateRxUSBOut();
+        }
+        USBSERIAL.print("rxUSBOutCal: ");
+        USBSERIAL.println(c->rxUSBOutCal);
+        break;
+      }
+      break;
+    }
+    break;
+
+    case 't': 
+    case 'T':
+    //TX audio parameters
+    switch(subcmd) {
+      case 'm':
+      case 'M':
+      // Mic input
+      switch(parm) {
+        case 'g':
+        case 'G':
+        // mic gain
+        if (set_value) {
+          c->txMicInGain = int(value);
+          updateTxMicIn();
+        }
+        USBSERIAL.print("txMicInGain: ");
+        USBSERIAL.println(c->txMicInGain);
+        break;
+
+        case 'v':
+        case 'V':
+        // volume
+        if (set_value) {
+          c->txMicInVol = value;
+          updateTxMicIn();
+        }
+        USBSERIAL.print("txMicInVol: ");
+        USBSERIAL.println(c->txMicInVol);
+        break;
+
+        case 'c':
+        case 'C':
+        // calibration
+        if (set_value) {
+          c->txMicInCal = value;
+          updateTxMicIn();
+        }
+        USBSERIAL.print("txMicInCal: ");
+        USBSERIAL.println(c->txMicInCal);
+        break;
+      }
+      break;
+
+      case 'l':
+      case 'L':
+      // Line input
+      switch(parm) {
+        case 'l':
+        case 'L':
+        // level
+        if (set_value) {
+          c->txLineInLevel = int(value);
+          updateTxLineIn();
+        }
+        USBSERIAL.print("txLineInLevel: ");
+        USBSERIAL.println(c->txLineInLevel);
+        break;
+
+        case 'v':
+        case 'V':
+        // volume
+        if (set_value) {
+          c->txLineInVol = value;
+          updateTxLineIn();
+        }
+        USBSERIAL.print("txLineInVol: ");
+        USBSERIAL.println(c->txLineInVol);
+        break;
+
+        case 'c':
+        case 'C':
+        // calibration
+        if (set_value) {
+          c->txLineInCal = value;
+          updateTxLineIn();
+        }
+        USBSERIAL.print("txLineInCal: ");
+        USBSERIAL.println(c->txLineInCal);
+        break;
+      }
+      break;
+
+      case 'u':
+      case 'U':
+      // USB input
+      switch(parm) {
+        case 'v':
+        case 'V':
+        // volume
+        if (set_value) {
+          c->txUSBInVol = value;
+          updateTxUSBIn();
+        }
+        USBSERIAL.print("txUSBInVol: ");
+        USBSERIAL.println(c->txUSBInVol);
+        break;
+
+        case 'c':
+        case 'C':
+        // calibration
+        if (set_value) {
+          c->txUSBInCal = value;
+          updateTxUSBIn();
+        }
+        USBSERIAL.print("txUSBInCal: ");
+        USBSERIAL.println(c->txUSBInCal);
+        break;
+      }
+      break;
+
+      case 'r':
+      case 'R':
+      // Rig output
+      switch(parm) {
+        case 'l':
+        case 'L':
+        // level
+        if (set_value) {
+          c->txRigOutLevel = int(value);
+          updateTxRigOut();
+        }
+        USBSERIAL.print("txRigOutLevel: ");
+        USBSERIAL.println(c->txRigOutLevel);
+        break;
+
+        case 'c':
+        case 'C':
+        // calibration
+        if (set_value) {
+          c->txRigOutCal = value;
+          updateTxRigOut();
+        }
+        USBSERIAL.print("txRigOutCal: ");
+        USBSERIAL.println(c->txRigOutCal);
+        break;
+      }
+      break;
+    }
+    break;
+  }  
+}
+
 //======================================================================
 // EOF
 //======================================================================
diff --git a/cat.h b/cat.h
index a7fc5ca..c25ad0a 100644
--- a/cat.h
+++ b/cat.h
@@ -5,6 +5,8 @@
 #ifndef __iop_cat_h__
 #define __iop_cat_h__
 
+#include "config.h"
+
 #define USBSERIAL Serial
 #define HWSERIAL Serial1
 
diff --git a/cat.ino b/cat.ino
index d36fe05..484f647 100644
--- a/cat.ino
+++ b/cat.ino
@@ -33,9 +33,11 @@ void initCAT(long baud, int portConfig)
   USBSERIAL.begin(baud);
   USBSERIAL.flush();
 
+#if not defined(FACTORY_CALIBRATION)
   // CAT with Raduino via UART
   HWSERIAL.begin(baud, portConfig);
   USBSERIAL.flush();
+#endif
 }
 
 //======================================================================
@@ -46,6 +48,35 @@ void processIOPCommand(const byte* buf, int len)
 
 //======================================================================
 
+void processCalCommand(const char* buf)
+{
+  int count;
+  char cmd;
+  char subcmd;
+  char parm;
+  float value;
+  
+  count = sscanf(buf, "%1c %1c %1c %f", &cmd, &subcmd, &parm, &value);
+
+  if (count < 3) {
+    USBSERIAL.println("Calibration: invalid command");
+  } else {    
+    switch(cmd) {
+      case 'r':
+      case 'R':
+      case 't':
+      case 'T':
+      audioCalibrate(&iopConfig, cmd, subcmd, parm, value, (count == 4));
+      break;
+
+      default:
+      USBSERIAL.println("Calibration: invalid command");
+    }
+  }
+}
+
+//======================================================================
+
 enum serial_mode_t {
   NORMAL = 0,
   CAT_MODE,
@@ -57,7 +88,8 @@ enum serial_mode_t {
 int readLength = 0;
 
 int cmdLength = 0;
-byte cmdBuffer[16];
+byte cmdBuffer[16]; 
+char cmdString[17]; // added a char for null termination when required
 
 uint16_t eepromStartIndex;
 uint16_t eepromReadLength;
@@ -72,6 +104,34 @@ void serviceCAT()
   // read from the USB serial, pass through to UART serial
   for (int i = 0; i < USBSERIAL.available(); i++) {
     incomingByte = USBSERIAL.read();
+
+#if defined(FACTORY_CALIBRATION)
+    // unless we're in factory calibration mode, in which case we're going
+    // to process calibration commands...    
+    switch(incomingByte) {
+      case ';':
+      cmdString[cmdLength] = '\0';
+      if (cmdLength > 0) {
+        processCalCommand(cmdString);
+        cmdLength = 0;
+      }
+      break;
+
+      case '\n':
+      case '\r':
+      cmdString[0] = '\0';
+      cmdLength = 0;
+      break;
+
+      default:
+      cmdString[cmdLength++] = char(incomingByte);
+      if (cmdLength == 16) {
+        cmdString[cmdLength] = '\0';
+        processCalCommand(cmdString);
+        cmdLength = 0;
+      }
+    } 
+#else
     HWSERIAL.write(incomingByte);
   }
 
@@ -179,6 +239,7 @@ void serviceCAT()
       // should never happen...
       break;
     }
+#endif
   }
 }
 
diff --git a/eeprom.h b/eeprom.h
index 4e17341..5a594b9 100644
--- a/eeprom.h
+++ b/eeprom.h
@@ -5,6 +5,8 @@
 #ifndef __iop_eeprom_h__
 #define __iop_eeprom_h__
 
+#include "config.h"
+
 #endif
 
 //======================================================================
diff --git a/ubitx_iop.h b/ubitx_iop.h
index 71d8922..fd6cef3 100644
--- a/ubitx_iop.h
+++ b/ubitx_iop.h
@@ -5,6 +5,7 @@
 #ifndef __ubitx_iop_h__
 #define __ubitx_iop_h__
 
+#include "config.h"
 #include "audio.h"
 #include "cat.h"
 #include "eeprom.h"
@@ -18,54 +19,7 @@ enum RigMode {
   MODE_CW,
 };
 
-// IOPConfig
-// Used to store configuration parameters during runtime, as well as to
-// save them to EEPROM.
-//
-// NOTE:  Need to put version info and a version check here.
-struct IOPConfig {
-
-  // RECEIVE PARAMETERS
-
-  // rig-in parameters (RX)
-  uint8_t rxRigInLevel   = 5;
-  float   rxRigInVol     = 1.0;
-  float   rxRigInCal     = 1.0;
-  // USB-in parameters (RX) - debug/monitor use only
-  bool    rxUSBInEnable  = false;
-  float   rxUSBInVol     = 1.0;
-  float   rxUSBInCal     = 1.0;
-  // speaker-out (DAC) parameters (RX)
-  float   rxSpkrOutCal   = 1.0;
-  // line-out parameters (RX)
-  uint8_t rxLineOutLevel = 29;
-  float   rxLineOutCal   = 1.0;
-  // USB-out parameters (RX)
-  float   rxUSBOutCal    = 1.0;
-
-  // TRANSMIT PARAMETERS
-
-  // microphone-in parameters (TX)
-  uint8_t txMicInGain    = 32;
-  float   txMicInVol     = 1.0;
-  float   txMicInCal     = 1.0;
-  // line-in parameters (TX)
-  uint8_t txLineInLevel  = 5;
-  float   txLineInVol    = 1.0;
-  float   txLineInCal    = 1.0;
-  // USB-in parameters (TX)
-  float   txUSBInVol     = 1.0;
-  float   txUSBInCal     = 1.0;
-  // rig-out parameters (TX)
-  uint8_t txRigOutLevel  = 29;
-  float   txRigOutCal    = 1.0;
-  // USB-out parameters (TX)- debug/monitor use only
-  bool    txUSBOutEnable = true;
-  float   txUSBOutCal    = 1.0; 
-};
-
 extern RigMode rigMode;
-extern IOPConfig iopConfig;
 
 #endif