fix: improved 24hr cycle via scheduler. Should help prevent issues with DLs.

backend/models.py

@@ -229,7 +229,7 @@ class ScheduledAction(Base):
     location_id = Column(String, nullable=False, index=True)  # FK to MonitoringLocation.id
     unit_id = Column(String, nullable=True, index=True)  # FK to RosterUnit.id (nullable if location-based)
 
-    action_type = Column(String, nullable=False)  # start, stop, download, calibrate
+    action_type = Column(String, nullable=False)  # start, stop, download, cycle, calibrate
     device_type = Column(String, nullable=False)  # "slm" | "seismograph"
 
     scheduled_time = Column(DateTime, nullable=False, index=True)

backend/routers/modem_dashboard.py

@@ -284,3 +284,146 @@ async def get_modem_diagnostics(modem_id: str, db: Session = Depends(get_db)):
         "carrier": None,
         "connection_type": None  # LTE, 5G, etc.
     }
+
+
+@router.get("/{modem_id}/pairable-devices")
+async def get_pairable_devices(
+    modem_id: str,
+    db: Session = Depends(get_db),
+    search: str = Query(None),
+    hide_paired: bool = Query(True)
+):
+    """
+    Get list of devices (seismographs and SLMs) that can be paired with this modem.
+    Used by the device picker modal in unit_detail.html.
+    """
+    # Check modem exists
+    modem = db.query(RosterUnit).filter_by(id=modem_id, device_type="modem").first()
+    if not modem:
+        return {"status": "error", "detail": f"Modem {modem_id} not found"}
+
+    # Query seismographs and SLMs
+    query = db.query(RosterUnit).filter(
+        RosterUnit.device_type.in_(["seismograph", "sound_level_meter"]),
+        RosterUnit.retired == False
+    )
+
+    # Filter by search term if provided
+    if search:
+        search_term = f"%{search}%"
+        query = query.filter(
+            (RosterUnit.id.ilike(search_term)) |
+            (RosterUnit.project_id.ilike(search_term)) |
+            (RosterUnit.location.ilike(search_term)) |
+            (RosterUnit.address.ilike(search_term)) |
+            (RosterUnit.note.ilike(search_term))
+        )
+
+    devices = query.order_by(
+        RosterUnit.deployed.desc(),
+        RosterUnit.device_type.asc(),
+        RosterUnit.id.asc()
+    ).all()
+
+    # Build device list
+    device_list = []
+    for device in devices:
+        # Skip already paired devices if hide_paired is True
+        is_paired_to_other = (
+            device.deployed_with_modem_id is not None and
+            device.deployed_with_modem_id != modem_id
+        )
+        is_paired_to_this = device.deployed_with_modem_id == modem_id
+
+        if hide_paired and is_paired_to_other:
+            continue
+
+        device_list.append({
+            "id": device.id,
+            "device_type": device.device_type,
+            "deployed": device.deployed,
+            "project_id": device.project_id,
+            "location": device.location or device.address,
+            "note": device.note,
+            "paired_modem_id": device.deployed_with_modem_id,
+            "is_paired_to_this": is_paired_to_this,
+            "is_paired_to_other": is_paired_to_other
+        })
+
+    return {"devices": device_list, "modem_id": modem_id}
+
+
+@router.post("/{modem_id}/pair")
+async def pair_device_to_modem(
+    modem_id: str,
+    db: Session = Depends(get_db),
+    device_id: str = Query(..., description="ID of the device to pair")
+):
+    """
+    Pair a device (seismograph or SLM) to this modem.
+    Updates the device's deployed_with_modem_id field.
+    """
+    # Check modem exists
+    modem = db.query(RosterUnit).filter_by(id=modem_id, device_type="modem").first()
+    if not modem:
+        return {"status": "error", "detail": f"Modem {modem_id} not found"}
+
+    # Find the device
+    device = db.query(RosterUnit).filter(
+        RosterUnit.id == device_id,
+        RosterUnit.device_type.in_(["seismograph", "sound_level_meter"]),
+        RosterUnit.retired == False
+    ).first()
+    if not device:
+        return {"status": "error", "detail": f"Device {device_id} not found"}
+
+    # Unpair any device currently paired to this modem
+    currently_paired = db.query(RosterUnit).filter(
+        RosterUnit.deployed_with_modem_id == modem_id
+    ).all()
+    for paired_device in currently_paired:
+        paired_device.deployed_with_modem_id = None
+
+    # Pair the new device
+    device.deployed_with_modem_id = modem_id
+    db.commit()
+
+    return {
+        "status": "success",
+        "modem_id": modem_id,
+        "device_id": device_id,
+        "message": f"Device {device_id} paired to modem {modem_id}"
+    }
+
+
+@router.post("/{modem_id}/unpair")
+async def unpair_device_from_modem(modem_id: str, db: Session = Depends(get_db)):
+    """
+    Unpair any device currently paired to this modem.
+    """
+    # Check modem exists
+    modem = db.query(RosterUnit).filter_by(id=modem_id, device_type="modem").first()
+    if not modem:
+        return {"status": "error", "detail": f"Modem {modem_id} not found"}
+
+    # Find and unpair device
+    device = db.query(RosterUnit).filter(
+        RosterUnit.deployed_with_modem_id == modem_id
+    ).first()
+
+    if device:
+        old_device_id = device.id
+        device.deployed_with_modem_id = None
+        db.commit()
+        return {
+            "status": "success",
+            "modem_id": modem_id,
+            "unpaired_device_id": old_device_id,
+            "message": f"Device {old_device_id} unpaired from modem {modem_id}"
+        }
+
+    return {
+        "status": "success",
+        "modem_id": modem_id,
+        "message": "No device was paired to this modem"
+    }

backend/services/alert_service.py

@@ -199,7 +199,7 @@ class AlertService:
 
         Args:
             schedule_id: The ScheduledAction or RecurringSchedule ID
-            action_type: start, stop, download
+            action_type: start, stop, download, cycle
             unit_id: Related unit
             error_message: Error from execution
             project_id: Related project
@@ -235,7 +235,7 @@ class AlertService:
 
         Args:
             schedule_id: The ScheduledAction ID
-            action_type: start, stop, download
+            action_type: start, stop, download, cycle
             unit_id: Related unit
             project_id: Related project
             location_id: Related location

backend/services/recurring_schedule_service.py

@@ -384,73 +384,33 @@ class RecurringScheduleService:
             if cycle_utc <= now_utc:
                 continue
 
-            # Check if action already exists
+            # Check if cycle action already exists
-            if self._action_exists(schedule.project_id, schedule.location_id, "stop", cycle_utc):
+            if self._action_exists(schedule.project_id, schedule.location_id, "cycle", cycle_utc):
                 continue
 
-            # Build notes with metadata
+            # Build notes with metadata for cycle action
-            stop_notes = json.dumps({
+            cycle_notes = json.dumps({
                 "schedule_name": schedule.name,
                 "schedule_id": schedule.id,
                 "cycle_type": "daily",
+                "include_download": schedule.include_download,
+                "auto_increment_index": schedule.auto_increment_index,
             })
 
-            # Create STOP action
+            # Create single CYCLE action that handles stop -> download -> start
-            stop_action = ScheduledAction(
+            # The scheduler's _execute_cycle method handles the full workflow with delays
+            cycle_action = ScheduledAction(
                 id=str(uuid.uuid4()),
                 project_id=schedule.project_id,
                 location_id=schedule.location_id,
                 unit_id=unit_id,
-                action_type="stop",
+                action_type="cycle",
                 device_type=schedule.device_type,
                 scheduled_time=cycle_utc,
                 execution_status="pending",
-                notes=stop_notes,
+                notes=cycle_notes,
             )
-            actions.append(stop_action)
+            actions.append(cycle_action)
-
-            # Create DOWNLOAD action if enabled (1 minute after stop)
-            if schedule.include_download:
-                download_time = cycle_utc + timedelta(minutes=1)
-                download_notes = json.dumps({
-                    "schedule_name": schedule.name,
-                    "schedule_id": schedule.id,
-                    "cycle_type": "daily",
-                })
-                download_action = ScheduledAction(
-                    id=str(uuid.uuid4()),
-                    project_id=schedule.project_id,
-                    location_id=schedule.location_id,
-                    unit_id=unit_id,
-                    action_type="download",
-                    device_type=schedule.device_type,
-                    scheduled_time=download_time,
-                    execution_status="pending",
-                    notes=download_notes,
-                )
-                actions.append(download_action)
-
-            # Create START action (2 minutes after stop, or 1 minute after download)
-            start_offset = 2 if schedule.include_download else 1
-            start_time = cycle_utc + timedelta(minutes=start_offset)
-            start_notes = json.dumps({
-                "schedule_name": schedule.name,
-                "schedule_id": schedule.id,
-                "cycle_type": "daily",
-                "auto_increment_index": schedule.auto_increment_index,
-            })
-            start_action = ScheduledAction(
-                id=str(uuid.uuid4()),
-                project_id=schedule.project_id,
-                location_id=schedule.location_id,
-                unit_id=unit_id,
-                action_type="start",
-                device_type=schedule.device_type,
-                scheduled_time=start_time,
-                execution_status="pending",
-                notes=start_notes,
-            )
-            actions.append(start_action)
 
         return actions
 

backend/services/scheduler.py

@@ -185,6 +185,8 @@ class SchedulerService:
                 response = await self._execute_stop(action, unit_id, db)
             elif action.action_type == "download":
                 response = await self._execute_download(action, unit_id, db)
+            elif action.action_type == "cycle":
+                response = await self._execute_cycle(action, unit_id, db)
             else:
                 raise Exception(f"Unknown action type: {action.action_type}")
 
@@ -375,8 +377,13 @@ class SchedulerService:
             f"{location.name}/session-{session_timestamp}/"
         )
 
-        # Step 1: Enable FTP on device
+        # Step 1: Disable FTP first to reset any stale connection state
-        logger.info(f"Enabling FTP on {unit_id} for download")
+        # Then enable FTP on device
+        logger.info(f"Resetting FTP on {unit_id} for download (disable then enable)")
+        try:
+            await self.device_controller.disable_ftp(unit_id, action.device_type)
+        except Exception as e:
+            logger.warning(f"FTP disable failed (may already be off): {e}")
         await self.device_controller.enable_ftp(unit_id, action.device_type)
 
         # Step 2: Download current measurement folder
@@ -397,6 +404,200 @@ class SchedulerService:
             "device_response": response,
         }
 
+    async def _execute_cycle(
+        self,
+        action: ScheduledAction,
+        unit_id: str,
+        db: Session,
+    ) -> Dict[str, Any]:
+        """Execute a full 'cycle' action: stop -> download -> start.
+
+        This combines stop, download, and start into a single action with
+        appropriate delays between steps to ensure device stability.
+
+        Workflow:
+        0. Pause background polling to prevent command conflicts
+        1. Stop measurement (wait 10s)
+        2. Disable FTP to reset state (wait 10s)
+        3. Enable FTP (wait 10s)
+        4. Download current measurement folder
+        5. Wait 30s for device to settle
+        6. Start new measurement cycle
+        7. Re-enable background polling
+
+        Total time: ~70-90 seconds depending on download size
+        """
+        logger.info(f"[CYCLE] === Starting full cycle for {unit_id} ===")
+
+        result = {
+            "status": "cycle_complete",
+            "steps": {},
+            "old_session_id": None,
+            "new_session_id": None,
+            "polling_paused": False,
+        }
+
+        # Step 0: Pause background polling for this device to prevent command conflicts
+        # NL-43 devices only support one TCP connection at a time
+        logger.info(f"[CYCLE] Step 0: Pausing background polling for {unit_id}")
+        polling_was_enabled = False
+        try:
+            if action.device_type == "slm":
+                # Get current polling state to restore later
+                from backend.services.slmm_client import get_slmm_client
+                slmm = get_slmm_client()
+                try:
+                    polling_config = await slmm.get_device_polling_config(unit_id)
+                    polling_was_enabled = polling_config.get("poll_enabled", False)
+                except Exception:
+                    polling_was_enabled = True  # Assume enabled if can't check
+
+                # Disable polling during cycle
+                await slmm.update_device_polling_config(unit_id, poll_enabled=False)
+                result["polling_paused"] = True
+                logger.info(f"[CYCLE] Background polling paused for {unit_id}")
+        except Exception as e:
+            logger.warning(f"[CYCLE] Failed to pause polling (continuing anyway): {e}")
+
+        try:
+            # Step 1: Stop measurement
+            logger.info(f"[CYCLE] Step 1/7: Stopping measurement on {unit_id}")
+            try:
+                stop_response = await self.device_controller.stop_recording(unit_id, action.device_type)
+                result["steps"]["stop"] = {"success": True, "response": stop_response}
+                logger.info(f"[CYCLE] Measurement stopped, waiting 10s...")
+            except Exception as e:
+                logger.warning(f"[CYCLE] Stop failed (may already be stopped): {e}")
+                result["steps"]["stop"] = {"success": False, "error": str(e)}
+
+            await asyncio.sleep(10)
+
+            # Step 2: Disable FTP to reset any stale state
+            logger.info(f"[CYCLE] Step 2/7: Disabling FTP on {unit_id}")
+            try:
+                await self.device_controller.disable_ftp(unit_id, action.device_type)
+                result["steps"]["ftp_disable"] = {"success": True}
+                logger.info(f"[CYCLE] FTP disabled, waiting 10s...")
+            except Exception as e:
+                logger.warning(f"[CYCLE] FTP disable failed (may already be off): {e}")
+                result["steps"]["ftp_disable"] = {"success": False, "error": str(e)}
+
+            await asyncio.sleep(10)
+
+            # Step 3: Enable FTP
+            logger.info(f"[CYCLE] Step 3/7: Enabling FTP on {unit_id}")
+            try:
+                await self.device_controller.enable_ftp(unit_id, action.device_type)
+                result["steps"]["ftp_enable"] = {"success": True}
+                logger.info(f"[CYCLE] FTP enabled, waiting 10s...")
+            except Exception as e:
+                logger.error(f"[CYCLE] FTP enable failed: {e}")
+                result["steps"]["ftp_enable"] = {"success": False, "error": str(e)}
+                # Continue anyway - download will fail but we can still try to start
+
+            await asyncio.sleep(10)
+
+            # Step 4: Download current measurement folder
+            logger.info(f"[CYCLE] Step 4/7: Downloading measurement data from {unit_id}")
+            location = db.query(MonitoringLocation).filter_by(id=action.location_id).first()
+            project = db.query(Project).filter_by(id=action.project_id).first()
+
+            if location and project:
+                session_timestamp = datetime.utcnow().strftime("%Y-%m-%d-%H%M")
+                location_type_dir = "sound" if action.device_type == "slm" else "vibration"
+                destination_path = (
+                    f"data/Projects/{project.id}/{location_type_dir}/"
+                    f"{location.name}/session-{session_timestamp}/"
+                )
+
+                try:
+                    download_response = await self.device_controller.download_files(
+                        unit_id,
+                        action.device_type,
+                        destination_path,
+                        files=None,
+                    )
+                    result["steps"]["download"] = {"success": True, "response": download_response}
+                    logger.info(f"[CYCLE] Download complete")
+                except Exception as e:
+                    logger.error(f"[CYCLE] Download failed: {e}")
+                    result["steps"]["download"] = {"success": False, "error": str(e)}
+            else:
+                result["steps"]["download"] = {"success": False, "error": "Project or location not found"}
+
+            # Close out the old recording session
+            active_session = db.query(RecordingSession).filter(
+                and_(
+                    RecordingSession.location_id == action.location_id,
+                    RecordingSession.unit_id == unit_id,
+                    RecordingSession.status == "recording",
+                )
+            ).first()
+
+            if active_session:
+                active_session.stopped_at = datetime.utcnow()
+                active_session.status = "completed"
+                active_session.duration_seconds = int(
+                    (active_session.stopped_at - active_session.started_at).total_seconds()
+                )
+                result["old_session_id"] = active_session.id
+
+            # Step 5: Wait for device to settle before starting new measurement
+            logger.info(f"[CYCLE] Step 5/7: Waiting 30s for device to settle...")
+            await asyncio.sleep(30)
+
+            # Step 6: Start new measurement cycle
+            logger.info(f"[CYCLE] Step 6/7: Starting new measurement on {unit_id}")
+            try:
+                cycle_response = await self.device_controller.start_cycle(
+                    unit_id,
+                    action.device_type,
+                    sync_clock=True,
+                )
+                result["steps"]["start"] = {"success": True, "response": cycle_response}
+
+                # Create new recording session
+                new_session = RecordingSession(
+                    id=str(uuid.uuid4()),
+                    project_id=action.project_id,
+                    location_id=action.location_id,
+                    unit_id=unit_id,
+                    session_type="sound" if action.device_type == "slm" else "vibration",
+                    started_at=datetime.utcnow(),
+                    status="recording",
+                    session_metadata=json.dumps({
+                        "scheduled_action_id": action.id,
+                        "cycle_response": cycle_response,
+                        "action_type": "cycle",
+                    }),
+                )
+                db.add(new_session)
+                result["new_session_id"] = new_session.id
+
+                logger.info(f"[CYCLE] New measurement started, session {new_session.id}")
+
+            except Exception as e:
+                logger.error(f"[CYCLE] Start failed: {e}")
+                result["steps"]["start"] = {"success": False, "error": str(e)}
+                raise  # Re-raise to mark the action as failed
+
+        finally:
+            # Step 7: Re-enable background polling (always runs, even on failure)
+            if result.get("polling_paused") and polling_was_enabled:
+                logger.info(f"[CYCLE] Step 7/7: Re-enabling background polling for {unit_id}")
+                try:
+                    if action.device_type == "slm":
+                        from backend.services.slmm_client import get_slmm_client
+                        slmm = get_slmm_client()
+                        await slmm.update_device_polling_config(unit_id, poll_enabled=True)
+                        logger.info(f"[CYCLE] Background polling re-enabled for {unit_id}")
+                except Exception as e:
+                    logger.error(f"[CYCLE] Failed to re-enable polling: {e}")
+                    # Don't raise - cycle completed, just log the error
+
+        logger.info(f"[CYCLE] === Cycle complete for {unit_id} ===")
+        return result
+
     # ========================================================================
     # Recurring Schedule Generation
     # ========================================================================

backend/services/slmm_client.py

@@ -109,7 +109,8 @@ class SLMMClient:
                 f"SLMM operation failed: {error_detail}"
             )
         except Exception as e:
-            raise SLMMClientError(f"Unexpected error: {str(e)}")
+            error_msg = str(e) if str(e) else type(e).__name__
+            raise SLMMClientError(f"Unexpected error: {error_msg}")
 
     # ========================================================================
     # Unit Management
@@ -579,7 +580,13 @@ class SLMMClient:
         """
         # Get current index number from device
         index_info = await self.get_index_number(unit_id)
-        index_number = index_info.get("index_number", 0)
+        index_number_raw = index_info.get("index_number", 0)
+
+        # Convert to int - device returns string like "0000" or "0001"
+        try:
+            index_number = int(index_number_raw)
+        except (ValueError, TypeError):
+            index_number = 0
 
         # Format as Auto_XXXX folder name
         folder_name = f"Auto_{index_number:04d}"

templates/partials/modem_paired_device.html

@@ -2,7 +2,7 @@
 {% if device %}
 <div class="flex items-center gap-4 p-4 bg-green-50 dark:bg-green-900/20 rounded-lg">
     <div class="bg-green-100 dark:bg-green-900/30 p-3 rounded-lg">
-        {% if device.device_type == "slm" %}
+        {% if device.device_type == "slm" or device.device_type == "sound_level_meter" %}
         <svg class="w-6 h-6 text-green-600 dark:text-green-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
             <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 19v-6a2 2 0 00-2-2H5a2 2 0 00-2 2v6a2 2 0 002 2h2a2 2 0 002-2zm0 0V9a2 2 0 012-2h2a2 2 0 012 2v10m-6 0a2 2 0 002 2h2a2 2 0 002-2m0 0V5a2 2 0 012-2h2a2 2 0 012 2v14a2 2 0 01-2 2h-2a2 2 0 01-2-2z"></path>
         </svg>
@@ -18,7 +18,7 @@
             {{ device.id }}
         </a>
         <div class="flex items-center gap-2 mt-1 text-sm text-gray-600 dark:text-gray-400">
-            <span class="capitalize">{{ device.device_type }}</span>
+            <span class="capitalize">{{ device.device_type | replace("_", " ") }}</span>
             {% if device.project_id %}
                 <span class="text-gray-400">|</span>
                 <span>{{ device.project_id }}</span>
@@ -30,11 +30,17 @@
             {% endif %}
         </div>
     </div>
+    <div class="flex items-center gap-2">
+        <button onclick="openModemPairDeviceModal()"
+                class="px-3 py-1.5 text-sm bg-gray-100 hover:bg-gray-200 dark:bg-gray-700 dark:hover:bg-gray-600 text-gray-700 dark:text-gray-300 rounded-lg transition-colors">
+            Edit Pairing
+        </button>
         <a href="/unit/{{ device.id }}" class="text-gray-400 hover:text-seismo-orange transition-colors">
             <svg class="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                 <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"></path>
             </svg>
         </a>
+    </div>
 </div>
 {% else %}
 <div class="flex items-center gap-4 p-4 bg-gray-50 dark:bg-gray-800 rounded-lg">
@@ -47,5 +53,12 @@
         <p class="text-gray-600 dark:text-gray-400">No device currently paired</p>
         <p class="text-sm text-gray-500 dark:text-gray-500">This modem is available for assignment</p>
     </div>
+    <button onclick="openModemPairDeviceModal()"
+            class="px-4 py-2 text-sm bg-seismo-orange hover:bg-orange-600 text-white rounded-lg transition-colors flex items-center gap-2">
+        <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M13.828 10.172a4 4 0 00-5.656 0l-4 4a4 4 0 105.656 5.656l1.102-1.101m-.758-4.899a4 4 0 005.656 0l4-4a4 4 0 00-5.656-5.656l-1.1 1.1"></path>
+        </svg>
+        Pair Device
+    </button>
 </div>
 {% endif %}

templates/partials/projects/schedule_interval.html

@@ -114,7 +114,7 @@
             </div>
         </div>
         <p class="text-xs text-gray-400 dark:text-gray-500 mt-3" id="cycle-timing">
-            At <span id="preview-time">00:00</span>: Stop → Download (1 min) → Start (2 min)
+            At <span id="preview-time">00:00</span>: Stop → Download → Start (~70 sec total)
         </p>
     </div>
 </div>
@@ -132,12 +132,12 @@ document.getElementById('include_download').addEventListener('change', function(
         downloadStep.style.display = 'flex';
         downloadArrow.style.display = 'block';
         startStepNum.textContent = '3';
-        cycleTiming.innerHTML = `At <span id="preview-time">${timeValue}</span>: Stop → Download (1 min) → Start (2 min)`;
+        cycleTiming.innerHTML = `At <span id="preview-time">${timeValue}</span>: Stop → Download → Start (~70 sec total)`;
     } else {
         downloadStep.style.display = 'none';
         downloadArrow.style.display = 'none';
         startStepNum.textContent = '2';
-        cycleTiming.innerHTML = `At <span id="preview-time">${timeValue}</span>: Stop → Start (1 min)`;
+        cycleTiming.innerHTML = `At <span id="preview-time">${timeValue}</span>: Stop → Start (~40 sec total)`;
     }
 });
 

templates/unit_detail.html

@@ -1571,6 +1571,242 @@ function clearPairing(deviceType) {
 
     closePairDeviceModal();
 }
+
+// ===== Modem Pair Device Modal Functions (for modems to pick a device) =====
+let modemPairDevices = []; // Cache loaded devices
+let modemHasCurrentPairing = false;
+
+function openModemPairDeviceModal() {
+    const modal = document.getElementById('modemPairDeviceModal');
+    const searchInput = document.getElementById('modemPairDeviceSearch');
+
+    if (!modal) return;
+
+    modal.classList.remove('hidden');
+    if (searchInput) {
+        searchInput.value = '';
+        searchInput.focus();
+    }
+
+    // Reset checkboxes
+    document.getElementById('modemPairHidePaired').checked = true;
+    document.getElementById('modemPairShowSeismo').checked = true;
+    document.getElementById('modemPairShowSLM').checked = true;
+
+    // Load available devices
+    loadPairableDevices();
+}
+
+function closeModemPairDeviceModal() {
+    const modal = document.getElementById('modemPairDeviceModal');
+    if (modal) modal.classList.add('hidden');
+    modemPairDevices = [];
+}
+
+async function loadPairableDevices() {
+    const listContainer = document.getElementById('modemPairDeviceList');
+    listContainer.innerHTML = '<div class="text-center py-8"><div class="animate-spin inline-block w-6 h-6 border-2 border-seismo-orange border-t-transparent rounded-full"></div><p class="mt-2 text-sm text-gray-500">Loading devices...</p></div>';
+
+    try {
+        const response = await fetch(`/api/modem-dashboard/${unitId}/pairable-devices?hide_paired=false`);
+        if (!response.ok) throw new Error('Failed to load devices');
+
+        const data = await response.json();
+        modemPairDevices = data.devices || [];
+
+        // Check if modem has a current pairing
+        modemHasCurrentPairing = modemPairDevices.some(d => d.is_paired_to_this);
+        const unpairBtn = document.getElementById('modemUnpairBtn');
+        if (unpairBtn) {
+            unpairBtn.classList.toggle('hidden', !modemHasCurrentPairing);
+        }
+
+        if (modemPairDevices.length === 0) {
+            listContainer.innerHTML = '<p class="text-center py-8 text-gray-500">No devices found in roster</p>';
+            return;
+        }
+
+        renderModemPairDeviceList();
+    } catch (error) {
+        console.error('Failed to load pairable devices:', error);
+        listContainer.innerHTML = '<p class="text-center py-8 text-red-500">Failed to load devices</p>';
+    }
+}
+
+function filterModemPairDeviceList() {
+    renderModemPairDeviceList();
+}
+
+function renderModemPairDeviceList() {
+    const listContainer = document.getElementById('modemPairDeviceList');
+    const searchInput = document.getElementById('modemPairDeviceSearch');
+    const hidePairedCheckbox = document.getElementById('modemPairHidePaired');
+    const showSeismoCheckbox = document.getElementById('modemPairShowSeismo');
+    const showSLMCheckbox = document.getElementById('modemPairShowSLM');
+
+    const searchTerm = searchInput?.value?.toLowerCase() || '';
+    const hidePaired = hidePairedCheckbox?.checked ?? true;
+    const showSeismo = showSeismoCheckbox?.checked ?? true;
+    const showSLM = showSLMCheckbox?.checked ?? true;
+
+    // Filter devices
+    let filteredDevices = modemPairDevices.filter(device => {
+        // Filter by device type
+        if (device.device_type === 'seismograph' && !showSeismo) return false;
+        if (device.device_type === 'sound_level_meter' && !showSLM) return false;
+
+        // Hide devices paired to OTHER modems (but show unpaired and paired-to-this)
+        if (hidePaired && device.is_paired_to_other) return false;
+
+        // Search filter
+        if (searchTerm) {
+            const searchFields = [
+                device.id,
+                device.project_id || '',
+                device.location || '',
+                device.note || ''
+            ].join(' ').toLowerCase();
+            if (!searchFields.includes(searchTerm)) return false;
+        }
+
+        return true;
+    });
+
+    if (filteredDevices.length === 0) {
+        listContainer.innerHTML = '<p class="text-center py-8 text-gray-500">No devices match your criteria</p>';
+        return;
+    }
+
+    // Build device list HTML
+    let html = '<div class="divide-y divide-gray-200 dark:divide-gray-700">';
+    for (const device of filteredDevices) {
+        const deviceTypeLabel = device.device_type === 'sound_level_meter' ? 'SLM' : 'Seismograph';
+        const deviceTypeClass = device.device_type === 'sound_level_meter'
+            ? 'bg-purple-100 dark:bg-purple-900/30 text-purple-800 dark:text-purple-300'
+            : 'bg-blue-100 dark:bg-blue-900/30 text-blue-800 dark:text-blue-300';
+
+        const deployedBadge = device.deployed
+            ? '<span class="px-2 py-0.5 bg-green-100 dark:bg-green-900/30 text-green-800 dark:text-green-300 text-xs rounded">Deployed</span>'
+            : '<span class="px-2 py-0.5 bg-amber-100 dark:bg-amber-900/30 text-amber-800 dark:text-amber-300 text-xs rounded">Benched</span>';
+
+        let pairingBadge = '';
+        if (device.is_paired_to_this) {
+            pairingBadge = '<span class="px-2 py-0.5 bg-seismo-orange/20 text-seismo-orange text-xs rounded font-medium">Current</span>';
+        } else if (device.is_paired_to_other) {
+            pairingBadge = `<span class="px-2 py-0.5 bg-gray-200 dark:bg-gray-600 text-gray-600 dark:text-gray-300 text-xs rounded">Paired: ${device.paired_modem_id}</span>`;
+        }
+
+        const isCurrentlyPaired = device.is_paired_to_this;
+
+        html += `
+            <div class="px-6 py-3 hover:bg-gray-50 dark:hover:bg-slate-700 cursor-pointer transition-colors ${isCurrentlyPaired ? 'bg-seismo-orange/5' : ''}"
+                 onclick="selectDeviceForModem('${device.id}')">
+                <div class="flex items-center justify-between">
+                    <div class="flex-1 min-w-0">
+                        <div class="flex items-center gap-2">
+                            <span class="font-medium text-gray-900 dark:text-white">${device.id}</span>
+                            <span class="px-2 py-0.5 ${deviceTypeClass} text-xs rounded">${deviceTypeLabel}</span>
+                        </div>
+                        ${device.project_id ? `<div class="text-sm text-gray-500 dark:text-gray-400">${device.project_id}</div>` : ''}
+                        ${device.location ? `<div class="text-sm text-gray-500 dark:text-gray-400 truncate">${device.location}</div>` : ''}
+                    </div>
+                    <div class="flex items-center gap-2 ml-4">
+                        ${deployedBadge}
+                        ${pairingBadge}
+                    </div>
+                </div>
+            </div>
+        `;
+    }
+    html += '</div>';
+
+    listContainer.innerHTML = html;
+}
+
+async function selectDeviceForModem(deviceId) {
+    const listContainer = document.getElementById('modemPairDeviceList');
+
+    // Show loading state
+    listContainer.innerHTML = '<div class="text-center py-8"><div class="animate-spin inline-block w-6 h-6 border-2 border-seismo-orange border-t-transparent rounded-full"></div><p class="mt-2 text-sm text-gray-500">Pairing device...</p></div>';
+
+    try {
+        const response = await fetch(`/api/modem-dashboard/${unitId}/pair?device_id=${encodeURIComponent(deviceId)}`, {
+            method: 'POST'
+        });
+
+        const result = await response.json();
+
+        if (result.status === 'success') {
+            closeModemPairDeviceModal();
+            // Reload the paired device section
+            loadPairedDevice();
+            // Show success message (optional toast)
+            showToast(`Paired with ${deviceId}`, 'success');
+        } else {
+            listContainer.innerHTML = `<p class="text-center py-8 text-red-500">${result.detail || 'Failed to pair device'}</p>`;
+        }
+    } catch (error) {
+        console.error('Failed to pair device:', error);
+        listContainer.innerHTML = '<p class="text-center py-8 text-red-500">Failed to pair device</p>';
+    }
+}
+
+async function unpairDeviceFromModem() {
+    const listContainer = document.getElementById('modemPairDeviceList');
+
+    // Show loading state
+    listContainer.innerHTML = '<div class="text-center py-8"><div class="animate-spin inline-block w-6 h-6 border-2 border-seismo-orange border-t-transparent rounded-full"></div><p class="mt-2 text-sm text-gray-500">Unpairing device...</p></div>';
+
+    try {
+        const response = await fetch(`/api/modem-dashboard/${unitId}/unpair`, {
+            method: 'POST'
+        });
+
+        const result = await response.json();
+
+        if (result.status === 'success') {
+            closeModemPairDeviceModal();
+            // Reload the paired device section
+            loadPairedDevice();
+            // Show success message
+            if (result.unpaired_device_id) {
+                showToast(`Unpaired ${result.unpaired_device_id}`, 'success');
+            } else {
+                showToast('No device was paired', 'info');
+            }
+        } else {
+            listContainer.innerHTML = `<p class="text-center py-8 text-red-500">${result.detail || 'Failed to unpair device'}</p>`;
+        }
+    } catch (error) {
+        console.error('Failed to unpair device:', error);
+        listContainer.innerHTML = '<p class="text-center py-8 text-red-500">Failed to unpair device</p>';
+    }
+}
+
+// Simple toast function (if not already defined)
+function showToast(message, type = 'info') {
+    // Check if there's already a toast container
+    let toastContainer = document.getElementById('toast-container');
+    if (!toastContainer) {
+        toastContainer = document.createElement('div');
+        toastContainer.id = 'toast-container';
+        toastContainer.className = 'fixed bottom-4 right-4 z-50 space-y-2';
+        document.body.appendChild(toastContainer);
+    }
+
+    const toast = document.createElement('div');
+    const bgColor = type === 'success' ? 'bg-green-500' : type === 'error' ? 'bg-red-500' : 'bg-gray-700';
+    toast.className = `${bgColor} text-white px-4 py-2 rounded-lg shadow-lg transform transition-all duration-300 translate-x-0`;
+    toast.textContent = message;
+
+    toastContainer.appendChild(toast);
+
+    // Auto-remove after 3 seconds
+    setTimeout(() => {
+        toast.classList.add('opacity-0', 'translate-x-full');
+        setTimeout(() => toast.remove(), 300);
+    }, 3000);
+}
 </script>
 
 <!-- Pair Device Modal -->
@@ -1637,4 +1873,81 @@ function clearPairing(deviceType) {
 <!-- Include Project Create Modal for inline project creation -->
 {% include "partials/project_create_modal.html" %}
 
+<!-- Modem Pair Device Modal (for modems to pick a device) -->
+<div id="modemPairDeviceModal" class="hidden fixed inset-0 z-50 overflow-y-auto">
+    <div class="flex items-center justify-center min-h-screen px-4">
+        <!-- Backdrop -->
+        <div class="fixed inset-0 bg-black/50" onclick="closeModemPairDeviceModal()"></div>
+
+        <!-- Modal Content -->
+        <div class="relative bg-white dark:bg-slate-800 rounded-xl shadow-xl max-w-lg w-full max-h-[90vh] flex flex-col">
+            <!-- Header -->
+            <div class="flex items-center justify-between px-6 py-4 border-b border-gray-200 dark:border-gray-700">
+                <div>
+                    <h3 class="text-lg font-semibold text-gray-900 dark:text-white">Pair Device to Modem</h3>
+                    <p class="text-sm text-gray-500 dark:text-gray-400">Select a seismograph or SLM to pair</p>
+                </div>
+                <button onclick="closeModemPairDeviceModal()" class="text-gray-400 hover:text-gray-600 dark:hover:text-gray-300">
+                    <svg class="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12"></path>
+                    </svg>
+                </button>
+            </div>
+
+            <!-- Search and Filters -->
+            <div class="px-6 py-4 border-b border-gray-200 dark:border-gray-700 space-y-3">
+                <input type="text"
+                       placeholder="Search by ID, project, location..."
+                       class="w-full px-4 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-slate-700 text-gray-900 dark:text-white focus:ring-2 focus:ring-seismo-orange focus:border-transparent"
+                       id="modemPairDeviceSearch"
+                       autocomplete="off"
+                       oninput="filterModemPairDeviceList()">
+                <div class="flex items-center gap-4">
+                    <label class="flex items-center gap-2 text-sm text-gray-600 dark:text-gray-400 cursor-pointer">
+                        <input type="checkbox"
+                               id="modemPairHidePaired"
+                               onchange="filterModemPairDeviceList()"
+                               checked
+                               class="rounded border-gray-300 dark:border-gray-600 text-seismo-orange focus:ring-seismo-orange">
+                        Hide paired devices
+                    </label>
+                    <label class="flex items-center gap-2 text-sm text-gray-600 dark:text-gray-400 cursor-pointer">
+                        <input type="checkbox"
+                               id="modemPairShowSeismo"
+                               onchange="filterModemPairDeviceList()"
+                               checked
+                               class="rounded border-gray-300 dark:border-gray-600 text-seismo-orange focus:ring-seismo-orange">
+                        Seismographs
+                    </label>
+                    <label class="flex items-center gap-2 text-sm text-gray-600 dark:text-gray-400 cursor-pointer">
+                        <input type="checkbox"
+                               id="modemPairShowSLM"
+                               onchange="filterModemPairDeviceList()"
+                               checked
+                               class="rounded border-gray-300 dark:border-gray-600 text-seismo-orange focus:ring-seismo-orange">
+                        SLMs
+                    </label>
+                </div>
+            </div>
+
+            <!-- Device List -->
+            <div id="modemPairDeviceList" class="flex-1 overflow-y-auto max-h-80">
+                <!-- Populated by JavaScript -->
+            </div>
+
+            <!-- Footer -->
+            <div class="px-6 py-4 border-t border-gray-200 dark:border-gray-700 bg-gray-50 dark:bg-slate-900 flex gap-3">
+                <button onclick="unpairDeviceFromModem()"
+                        id="modemUnpairBtn"
+                        class="hidden px-4 py-2 bg-red-100 hover:bg-red-200 dark:bg-red-900/30 dark:hover:bg-red-900/50 text-red-700 dark:text-red-300 rounded-lg transition-colors">
+                    Unpair Current
+                </button>
+                <button onclick="closeModemPairDeviceModal()" class="flex-1 px-4 py-2 bg-gray-200 dark:bg-gray-700 hover:bg-gray-300 dark:hover:bg-gray-600 text-gray-700 dark:text-gray-300 rounded-lg transition-colors">
+                    Cancel
+                </button>
+            </div>
+        </div>
+    </div>
+</div>
+
 {% endblock %}