diff --git a/internal/api/device_manager.go b/internal/api/device_manager.go
index 8f5aa54..2c0fda3 100644
--- a/internal/api/device_manager.go
+++ b/internal/api/device_manager.go
@@ -126,6 +126,26 @@ func (dm *DeviceManager) Initialize() error {
 		dm.flexRadio.SetFrequencyChangeCallback(func(freqMHz float64) {
 			dm.handleFrequencyChange(freqMHz)
 		})
+
+		// Set callback to check if transmit is allowed (based on Ultrabeam motors)
+		dm.flexRadio.SetTransmitCheckCallback(func() bool {
+			// Get current Ultrabeam status
+			ubStatus, err := dm.ultrabeam.GetStatus()
+			if err != nil || ubStatus == nil {
+				// If we cannot get status, allow transmit (fail-safe)
+				return true
+			}
+
+			// Block transmit if motors are moving
+			motorsMoving := ubStatus.MotorsMoving != 0
+			if motorsMoving {
+				log.Printf("FlexRadio PTT check: Motors moving (bitmask=%d) - BLOCKING", ubStatus.MotorsMoving)
+			} else {
+				log.Printf("FlexRadio PTT check: Motors stopped - ALLOWING")
+			}
+
+			return !motorsMoving
+		})
 	}
 
 	// Initialize Solar data client
diff --git a/internal/devices/flexradio/flexradio.go b/internal/devices/flexradio/flexradio.go
index 276f714..625829e 100644
--- a/internal/devices/flexradio/flexradio.go
+++ b/internal/devices/flexradio/flexradio.go
@@ -29,15 +29,22 @@ type Client struct {
 	running  bool
 	stopChan chan struct{}
 
+	// Interlock
+	interlockID   string       // ID retourné par la radio (ex: "000000F4")
+	interlockName string       // Nom de notre interlock
+	interlockMu   sync.RWMutex // Protection pour l'ID
+
 	// Callbacks
-	onFrequencyChange func(freqMHz float64)
+	onFrequencyChange    func(freqMHz float64)
+	checkTransmitAllowed func() bool // Returns true if transmit allowed (motors not moving)
 }
 
 func New(host string, port int, interlockName string) *Client {
 	return &Client{
-		host:     host,
-		port:     port,
-		stopChan: make(chan struct{}),
+		host:          host,
+		port:          port,
+		interlockName: interlockName,
+		stopChan:      make(chan struct{}),
 		lastStatus: &Status{
 			Connected: false,
 		},
@@ -49,6 +56,11 @@ func (c *Client) SetFrequencyChangeCallback(callback func(freqMHz float64)) {
 	c.onFrequencyChange = callback
 }
 
+// SetTransmitCheckCallback sets the callback to check if transmit is allowed
+func (c *Client) SetTransmitCheckCallback(callback func() bool) {
+	c.checkTransmitAllowed = callback
+}
+
 func (c *Client) Connect() error {
 	c.connMu.Lock()
 	defer c.connMu.Unlock()
@@ -93,6 +105,12 @@ func (c *Client) Start() error {
 	// Start message listener
 	go c.messageLoop()
 
+	// Create interlock
+	log.Printf("FlexRadio: Creating interlock '%s'...", c.interlockName)
+	if err := c.createInterlock(); err != nil {
+		log.Printf("FlexRadio: Warning - failed to create interlock: %v", err)
+	}
+
 	// Subscribe to slice updates for frequency tracking
 	log.Println("FlexRadio: Subscribing to slice updates...")
 	_, err := c.sendCommand("sub slice all")
@@ -213,6 +231,7 @@ func (c *Client) messageLoop() {
 			continue
 		}
 
+		log.Printf("FlexRadio RX: %s", line)
 		c.handleMessage(line)
 	}
 
@@ -222,6 +241,7 @@ func (c *Client) messageLoop() {
 func (c *Client) handleMessage(msg string) {
 	// Response format: R<seq>|<status>|<data>
 	if strings.HasPrefix(msg, "R") {
+		c.handleResponse(msg)
 		return
 	}
 
@@ -244,6 +264,32 @@ func (c *Client) handleMessage(msg string) {
 	}
 }
 
+func (c *Client) handleResponse(msg string) {
+	// Format: R<seq>|<status>|<data>
+	// Example: R21|0|000000F4
+	parts := strings.SplitN(msg, "|", 3)
+	if len(parts) < 2 {
+		return
+	}
+
+	status := parts[1]
+	if status != "0" {
+		log.Printf("FlexRadio: Command error: status=%s, message=%s", status, msg)
+		return
+	}
+
+	// Check if this is interlock create response (has data in 3rd part)
+	if len(parts) >= 3 && parts[2] != "" {
+		interlockID := parts[2]
+
+		c.interlockMu.Lock()
+		c.interlockID = interlockID
+		c.interlockMu.Unlock()
+
+		log.Printf("FlexRadio: ✅ Interlock created successfully with ID: %s", interlockID)
+	}
+}
+
 func (c *Client) handleStatus(msg string) {
 	// Format: S<handle>|<key>=<value> ...
 	parts := strings.SplitN(msg, "|", 2)
@@ -286,6 +332,18 @@ func (c *Client) handleStatus(msg string) {
 			}
 		}
 	}
+	// Check for interlock PTT_REQUESTED
+	// Format: S0|interlock ... state=PTT_REQUESTED ...
+	if strings.Contains(msg, "interlock") {
+		if state, ok := statusMap["state"]; ok {
+			log.Printf("FlexRadio: Interlock state changed to: %s", state)
+
+			if state == "PTT_REQUESTED" {
+				// PTT requested - we MUST respond within 500ms!
+				c.handlePTTRequest()
+			}
+		}
+	}
 }
 
 func (c *Client) GetStatus() (*Status, error) {
@@ -304,3 +362,53 @@ func (c *Client) GetStatus() (*Status, error) {
 
 	return &status, nil
 }
+
+// createInterlock creates an interlock on the radio
+func (c *Client) createInterlock() error {
+	// Format: interlock create type=ANT name=<name> serial=ShackMaster
+	// Type ANT = External antenna controller (state always controlled by us)
+	cmd := fmt.Sprintf("interlock create type=ANT name=%s serial=ShackMaster", c.interlockName)
+
+	log.Printf("FlexRadio: Sending interlock create command: %s", cmd)
+
+	_, err := c.sendCommand(cmd)
+	if err != nil {
+		return fmt.Errorf("failed to send interlock create: %w", err)
+	}
+
+	// The response will be parsed in handleResponse()
+	// Format: R<seq>|0|<interlock_id> (ex: R21|0|000000F4)
+
+	return nil
+}
+
+// handlePTTRequest is called when FlexRadio sends PTT_REQUESTED
+// We MUST respond within 500ms with ready or not_ready
+func (c *Client) handlePTTRequest() {
+	log.Println("FlexRadio: 🔴 PTT REQUESTED - checking if transmit allowed...")
+
+	c.interlockMu.RLock()
+	interlockID := c.interlockID
+	c.interlockMu.RUnlock()
+
+	if interlockID == "" {
+		log.Println("FlexRadio: ⚠️  No interlock ID, cannot respond to PTT request!")
+		return
+	}
+
+	// Check if transmit is allowed via callback
+	allowed := true
+	if c.checkTransmitAllowed != nil {
+		allowed = c.checkTransmitAllowed()
+	}
+
+	if allowed {
+		log.Println("FlexRadio: ✅ Transmit ALLOWED - sending 'ready'")
+		cmd := fmt.Sprintf("interlock ready %s", interlockID)
+		c.sendCommand(cmd)
+	} else {
+		log.Println("FlexRadio: ❌ Transmit BLOCKED - sending 'not_ready'")
+		cmd := fmt.Sprintf("interlock not_ready %s", interlockID)
+		c.sendCommand(cmd)
+	}
+}