Vehicle theft, tracker removal, power interruption, and unauthorized use remain persistent security challenges for fleet operators, vehicle finance providers, rental and lease businesses, and recovery service providers.

ST35 is a Tamper-Resistant BLE Immobilizer Solution that pairs a compatible BLE-enabled ST SUNLAB tracking device with a relay unit installed separately in the engine compartment. Through encrypted BLE communication, the tracking device remotely controls the vehicle's ignition or starter circuit without any additional immobilizer signal wiring.

Its latching relay holds the last ON/OFF state without continuous coil power, while anti-tamper protection automatically immobilizes the vehicle if the main tracker is removed or its presence signal is no longer detected.

ST35 is more than a remote-controlled BLE relay. It is designed to address these security challenges.

Conventional immobilizer systems often connect the tracking device and the relay with direct wiring. If someone finds that wiring or the tracker, they can disconnect it or bypass the immobilizer circuit. This wiring also adds installation complexity.

Standard relays often need continuous coil power to hold their state. This makes resistance to power interruption and electrical tampering just as important.

An effective vehicle security system needs to do the following:

• Maintain the immobilizer state during power interruption
• Protect the vehicle even if the main tracker is removed or its presence signal is no longer detected
• Control vehicle ignition without additional signal wiring
• Reduce the risk of immobilizer detection, bypass, and tampering
• Support a wide range of vehicle electrical systems and engine compartment environments

• Latching Relay Immobilizer Control

  When the telematics platform sends an immobilizer command, the tracking device relays it to the ST35 over encrypted BLE.
  The ST35's internal latching relay then controls the ignition or starter circuit to enable or block engine start.
  The relay only needs coil power to change state, so it holds its last commanded position even during a brief power interruption.

• Automatic Anti-Tamper Protection

  The ST35 monitors whether the main BLE tracking device is present.
  If the tracker is removed or its presence signal is no longer detected, the ST35 automatically activates the immobilizer function to prevent unauthorized engine restart.

• Hidden Wireless Immobilizer Architecture

  The main tracking device can be installed inside the vehicle while the ST35 sits separately in the engine compartment. The two devices communicate over encrypted BLE.
  Without an additional immobilizer signal cable between the tracking device and ST35, and with the tracking and engine control components in different locations, the full security system becomes harder to find and bypass.

• Support for a Wide Range of Vehicles and Installation Environments

  The ST35 supports an 8 to 60V input range, IP67 protection, an operating temperature range of -30°C to +85°C (-22°F to +185°F), and internal NO/NC relay control.
  One model can cover passenger vehicles, light commercial vehicles, trucks, and other commercial equipment.

• BLE 5.3 Communication and FOTA Support

  The ST35 supports encrypted BLE 5.3 communication and receives firmware updates remotely through a compatible ST SUNLAB tracking device.

• Reduced Vehicle Loss and Recovery Risk

  Cutting power or removing the tracker does not simply reset the immobilizer protection.
  The ST35 helps maintain vehicle protection in these tampering scenarios, supporting vehicle finance companies and recovery service providers in reducing asset and recovery risk.

• More Value from Existing Tracker Deployments

  Operators can add the ST35 to a compatible ST SUNLAB tracker already in the field, without replacing the existing tracking hardware.
  This extends existing tracking deployments with immobilizer functionality and creates an additional security upgrade opportunity.

• Lower Operating Costs Through Installation Standardization

  The ST35 supports an 8 to 60V input range and connects wirelessly over BLE.
  This reduces the need for separate 12V and 24V variants and additional immobilizer signal wiring.
  A single ST35 model can therefore simplify installation planning, SKU management, and inventory across mixed vehicle fleets.

• Reduced Relay Stress and Maintenance Burden

  The latching relay only draws coil power when changing state, reducing continuous power consumption, heat generation, and electrical and thermal stress on the relay.
  This can help reduce maintenance burden and improve long-term operational reliability.

• Harder to Detect or Bypass

  The tracker and the immobilizer relay are installed in different locations in the vehicle. Finding one device does not immediately expose the other, making the complete security system harder to identify and disable.
  This provides an additional layer of protection against unauthorized vehicle use for rental, lease, finance, and fleet operations.

Vehicle Recovery & Anti-Theft | BHPH & Vehicle Finance | Rental & Lease | Fleet Management | Commercial Vehicle & Heavy Equipment

• 

  ST35

  • Compact, IP67-rated vehicle ignition controller
  • BLE 5.3 for wireless tracker integration
  • Customizable ignition on/off mode
  • Built for vehicle theft prevention
• 

  SD8000U

  • New cost-effective tracker series
  • Slim bar style design (0.65 in)
  • Wide power supply (DC 8–90V)
  • BLE 5.3 gateway
  • IP68-rated rugged design
• 

  ST8230

  • New compact cat. 1 bis tracker
  • Wide Input voltage range (DC 8-90V)
  • BLE 5.3 sensor scan
• 

  ST4315B

  • Rugged 6-pin wired GPS Tracker
  • BLE 5.3 sensor scan
  • Multiple optional models are available
  • IP67-rated rugged design
• 

  ST6560

  • Smaller Smarter Simpler OBDII Tracker
  • OBD-II / CAN Bus vehicle data access
  • J1939 / FMS support (heavy-duty)
  • Uninterrupted Tracking with Dead Reckoning
  • BLE 5.3 for sensor scanning