diff --git a/index.js b/index.js
index 954cf88..b6b99c9 100644
--- a/index.js
+++ b/index.js
@@ -127,6 +127,10 @@ class UnitConnection extends EventEmitter {
     this.client.write(new messages.SLVersionMessage().toBuffer());
   }
 
+  setCircuitState(controllerId, circuitId, circuitState) {
+    this.client.write(new messages.SLSetCircuitStateMessage(controllerId, circuitId, circuitState).toBuffer());
+  }
+
   onClientMessage(msg) {
     //console.log('received message of length ' + msg.length);
     if (msg.length < 4) {
@@ -163,6 +167,10 @@ class UnitConnection extends EventEmitter {
         //console.log("  it's version");
         this.emit('version', new messages.SLVersionMessage(msg));
         break;
+      case messages.SLSetCircuitStateMessage.getResponseId():
+        //console.log("  it's circuit toggle ack");
+        this.emit('circuitStateChanged', new messages.SLSetCircuitStateMessage());
+        break;
       default:
         //console.log("  it's unknown. type: " + msgType);
         break;
diff --git a/messages/SLMessage.js b/messages/SLMessage.js
old mode 100755
new mode 100644
index 48d2ab3..2d5b0b6
--- a/messages/SLMessage.js
+++ b/messages/SLMessage.js
@@ -10,6 +10,8 @@ exports.SLMessage = class SLMessage extends SmartBuffer {
   }
 
   toBuffer() {
+    this.encode();
+
     if (this._wroteSize === false) {
       this.insertInt32LE(this.length - 4, 4);
       this._wroteSize = true;
@@ -54,4 +56,8 @@ exports.SLMessage = class SLMessage extends SmartBuffer {
     this.messageId = this.readUInt16LE();
     this.dataLength = this.readInt32LE();
   }
+
+  encode() {
+
+  }
 }
diff --git a/messages/SLSetCircuitStateMessage.js b/messages/SLSetCircuitStateMessage.js
new file mode 100644
index 0000000..80361fb
--- /dev/null
+++ b/messages/SLSetCircuitStateMessage.js
@@ -0,0 +1,25 @@
+const SLMessage = require('./SLMessage.js').SLMessage;
+
+const MSG_ID = 12530;
+
+exports.SLSetCircuitStateMessage = class SLSetCircuitStateMessage extends SLMessage {
+  constructor(controllerId, circuitId, circuitState) {
+  	super(0, MSG_ID);
+
+  	this.controllerId = controllerId;
+  	this.circuitId = circuitId;
+  	this.circuitState = circuitState;
+  }
+
+  encode() {
+    this.writeInt32LE(this.controllerId || 0);
+    this.writeInt32LE(this.circuitId || 0);
+    this.writeInt32LE(this.circuitState || 0);
+
+    super.encode();
+  }
+
+  static getResponseId() {
+    return MSG_ID + 1;
+  }
+}
diff --git a/messages/index.js b/messages/index.js
old mode 100755
new mode 100644
index d7d7377..5337d18
--- a/messages/index.js
+++ b/messages/index.js
@@ -5,3 +5,4 @@ exports.SLLoginMessage = require("./SLLoginMessage.js").SLLoginMessage;
 exports.SLChemDataMessage = require("./SLChemDataMessage.js").SLChemDataMessage;
 exports.SLSaltCellConfigMessage = require("./SLSaltCellConfigMessage.js").SLSaltCellConfigMessage;
 exports.SLVersionMessage = require("./SLVersionMessage.js").SLVersionMessage;
+exports.SLSetCircuitStateMessage = require("./SLSetCircuitStateMessage.js").SLSetCircuitStateMessage;