STL Option Module [1204-3E]

The Satelles Satellite Time and Location (STL) signal is broadcast on Iridium satellites and offers a spoofing-resilient encrypted signal that is 1000x stronger than GNSS-based timing signals. Hence, it is difficult to jam, and it can be received indoors.

STL is a subscription-based service. Please contact Safran for details.

A SecureSync equipped with the STL 1204-3E option card can be operated with or without GPS, depending on your application, i.e. STL can be utilized as a backup, or as the only external timing source.

Note: Devices are shipped with the STL subscription deactivated. It is necessary to contact customer service to activate the subscription: US: +1 585 321 5800; France: +33 (0)1 64 53 3980.

For subscription renewal information, see Renewing Your STL Subscription

Hardware Installation

  1. If your STL option card was purchased together with a SecureSync unit, the card will be pre-installed in the unit. Proceed to Step 3.
  2. If you purchased your STL option card separately, you will need to install the card into the SecureSyncunit. For instructions, see the hard copy of the Option Card Installation Guide that shipped with the unit, or see the Field Installation instructions in the user manual.

    Note: The -3E card can be installed in any free card slot.

  3. Install the SecureSync unit in its assigned location e.g., in a server rack.
  4. Install the supplied STL satellite antenna: The antenna is designed for indoor use. The ideal location for the antenna is near the ceiling of the room in which your SecureSync unit is located, or near an outside wall. In general, a higher location is preferable over a lower location. Do not cover the antenna with electronic equipment or other metal objects.

    Note: The supplied antenna cable is 2.4 m (96") long. Longer cables are available upon request. The antenna does not require a separate power supply.

  5. Connect the antenna cable to the SecureSync unit via the SMA connector on the option card -3E rear plate. The SecureSync can be in a powered off or a powered on state during antenna installation.

    Model 1204-3E option card rear plate

    • If the unit is ON, verify that the BURST lamp is blinking.
    • If the unit is OFF, turn it on, and wait until the BURST lamp is blinking.

    If the BURST lamp is not blinking after the subscription has been activated, the STL receiver is not receiving an STL signal. Check the antenna cable and its connections, and the antenna location. Move the antenna to another location (higher or closer to an outside wall).

    Rear Plate LEDs:

    BURST: Indicates the incoming STL burst rate. A high burst rate (desired) is indicated by the LED flashing quickly.

    PPS: Indicates that the STL receiver is sending out a PPS signal to SecureSync. One (1) pulse per second means that the receiver is locked. NOTE: It can take approximately 10 minutes or longer until the receiver is locked. This depends on the burst rate (see Burst Rate.)

    Both LEDs have equivalent indicators in the Web UI STL 0 status window:

  6. Proceed with the SW configuration of the STL settings, as described below.

    Note: The RJ-45 MAINT. connector will not be needed for the STL configuration. Use this connector only if so requested by Safran Service personnel.

Configuring STL Settings

Note: If you do not yet have a subscription key, you will need to obtain one before continuing with installation. Please contact Safran customer service:

US: +1 585 321 5800; France: +33 (0)1 64 53 3980

Note: During the initial installation of a unit equipped with an STL card, the exact geographic position needs to be entered into the Web UI (see below). Should the unit be relocated at a later point in time, the position must be changed accordingly.

The STL option card 1204-3E is configured via the SecureSync Web UI. See The SecureSync Web UI for basic SecureSync setup and initial login information.

To configure STL settings:

  1. Log into the Web UI, and navigate to INTERFACES > OPTION CARDS: STL 0. The STL 0 status window will be displayed.
  2. In the STL 0 status window, click on the Edit button to open the STL 0 setup window.
  3. In the STL 0 setup window, you can configure the following parameters:

    • Subscription Key: [required] Enter the key obtained from customer service in order to activate STL access.
    • Latitude, Longitude, Altitude: [decimal degrees, meters] Actual geographic position of SecureSync's STL antenna. For help determining your actual position, see Determining Your Position.
    • Geolocation Mode: Static Known Position/Static Unknown Position [default]/Pseudo Static/Dynamic: This parameter refers to how the STL receiver handles position estimation. The default setting is recommended for most applications.
    • Sensitivity Level: [default = 40] This value determines the sensitivity of the STL receiver towards the STL signal bursts transmitted by the satellites. The lower the number, the more responsive the receiver will be to acknowledge the bursts. The default value is optimized for an indoor antenna. A higher value can be used for outdoor antenna installations (not typical). A value lower than (40) is not recommended.

  4. Assign the STL 0 reference a reference priority by navigating to MANAGEMENT > OTHER: Reference Priority.
  5. In the Configure Reference Priorities panel, click the + icon in the upper right corner. The Add Reference window will open.
  6. Select a Priority Level:
    1. If STL is to be used as a backup to GPS: Select a Priority Level of 2.
    2. If STL is the only reference: Select a Priority Level of 1.

    For Time and PPS, select STL 0. Click Submit.

  7. Verify your settings in the Reference Priority table, and ensure that the new reference is Enabled.

Reviewing the STL Status

Burst Rate

Satellites transmit the STL time and location data in bursts. The number of bursts per minute that the receiver detects is the burst rate, but only strong bursts have a quality high enough to be usable. Note that the burst rate changes over time due to the movement of the satellites and other factors.

The current strong burst rate is shown in the STL 0 status window (described above) and offers a good indication on the reception quality. Typically, a number of received strong bursts per minute is greater than 60, the location has sufficient STL service for the receiver to converge and provide a timing solution.

Strong Bursts Conditions Typically experienced ... Receiver lock status Troubleshooting
80+ Excellent, minimal signal attenuation … outdoors Short time to convergence No action required
35-55 Good, some signal attenuation … indoors near windows Short time to convergence No action required
15-30 Moderate, strong signal attenuation … indoors far from windows Longer time to convergence Wait a couple of minutes for better satellite geometry;
relocate antenna
5-15 Marginal, major signal attenuation … deep indoors Significantly longer time to convergence Wait several minutes for better satellite geometry;
relocate antenna
0 Poor, severe signal attenuation … very deep indoors No convergence Verify that STL service is enabled in your area;
wait several minuts for better satellite geometry;
relocate antenna

Note: The values shown above are only guidelines: Due to the dynamic nature of satellite signal characteristics over time, a specific burst threshold value does not guarantee a good receiver performance.


The specifications of the STL Option Module 1204-3E are:

  • Inputs: One STL antenna input, one Ethernet maintenance input
  • Antenna input connector: SMA
  • Maintenance connector: RJ45
  • Frequency band: 1626 MHz
  • Timing synchronization accuracy to UTC: ±500 ns (specified); ±200 ns (typical)
  • Coverage: Global
  • Time-to-first-fix (Timing): Several seconds (the PPS pulse will become available once the positioning fix has been obtained)
  • Jamming resilience: Signal is 30 to 40 dB stronger than GPS signal
  • Spoofing resilience: Encrypted signal
  • Maximum number of cards: 1
  • Ordering information:
    • STL module: 1204-3E
    • STL subscription (1 year): STL-SS-1Y

Model 1204-3E option card rear plate