As the drone industry shifts from simple radio-frequency (RF) controls to sophisticated, cellular-integrated ecosystems, the hardware involved has become increasingly complex. One term that often surfaces within the settings of high-end drone controllers and LTE-enabled modules is “Fixed Dialing Numbers” (FDN). While originally a feature of telecommunications, FDN has become a critical sub-topic for drone professionals who utilize cellular-enabled accessories to extend range, ensure data security, and maintain compliance with evolving airspace regulations.
Decoding Fixed Dialing Numbers (FDN) in the Context of Drone Hardware
Fixed Dialing Numbers (FDN) is a service mode of a Subscriber Identity Module (SIM) card that restricts outgoing communication to a specific list of pre-defined numbers. When FDN is activated on a SIM card inserted into a drone’s smart controller or an onboard LTE module, the device can only connect to the “phone numbers” or data endpoints explicitly allowed on the FDN list.
In the world of drone accessories, this isn’t just about making phone calls from a remote controller; it is about controlling the cellular handshake and data transmission pathways. Modern drone accessories, such as the DJI Cellular Dongle or the internal SIM slots of the Autel Smart Controller, rely on GSM standards. FDN serves as a hardware-level gatekeeper, ensuring that the cellular accessory does not communicate with unauthorized servers or consume data through unapproved channels.
The Mechanics of FDN and the SIM Card
The FDN feature is stored directly on the SIM card rather than the drone’s firmware. This means the restriction travels with the SIM. For drone operators, this is a vital distinction. If an operator moves a SIM card from a primary controller to a backup LTE module on a different aircraft, the FDN restrictions remain intact.
To enable or modify FDN, the user must possess the PIN2 code. This is a secondary security layer provided by the network carrier, separate from the standard PIN used to unlock the device. In professional drone accessories, having this secondary layer of authentication ensures that only the fleet manager or the authorized technician can alter the communication parameters of the drone’s connectivity modules.
How FDN Translates to Modern Drone Controllers
Most high-end drone controllers, such as the DJI RC Pro or the Parrot Skycontroller, are built on modified Android operating systems. Because they function essentially as specialized tablets with integrated joysticks, they inherit standard cellular protocols. When you insert a SIM card for real-time map loading or Remote ID transmission, the FDN setting appears in the “Network and Internet” settings of the controller’s interface.
For a drone pilot, activating FDN means that even if the controller is compromised or the SIM is removed and placed into a smartphone, it cannot be used to browse the open web or make unauthorized calls. It is locked down to the specific data gateways required for flight operations, such as the manufacturer’s cloud servers or private RTK (Real-Time Kinematic) network addresses.
The Critical Role of FDN in Enterprise and Industrial Drone Fleets
In industrial applications—such as power line inspections, search and rescue, or precision agriculture—drones are often treated as networked IoT (Internet of Things) devices. Fleet managers overseeing dozens of cellular-equipped drone accessories must account for both security and operational costs. FDN is one of the primary tools used to achieve this control.
Preventing Unauthorized Data Consumption
One of the most practical reasons for implementing FDN in drone accessories is cost management. High-bandwidth cellular data for drone video transmission can be expensive. If a SIM card is used without FDN, there is a risk that the background processes of the controller’s Android OS could download large system updates, stream high-definition content, or sync personal cloud accounts, quickly exhausting the data cap.
By using FDN, the operator ensures that the accessory only communicates with the specific IP addresses or SMS gateways necessary for flight telemetry and command-and-control. This “white-listing” approach is essential for businesses that deploy drones in remote areas where data roaming charges can be exorbitant.
Enhancing Fleet Security and Preventing SIM Misuse
Security is a paramount concern for enterprise drone operations. If a drone crashes in a public area or is stolen, the physical hardware is at risk, but so is the data connection. A SIM card from a drone’s LTE module is an easy target for theft. An attacker could remove the SIM and use it in a mobile hotspot to gain untraceable internet access on the company’s dime.
FDN acts as a robust deterrent. Without the PIN2 code, an unauthorized user cannot change the FDN list. If the SIM is placed in another device, it will still only attempt to “dial” or connect to the pre-approved drone telemetry servers. This effectively bricks the SIM card for any use other than its intended purpose, protecting the organization’s mobile accounts and ensuring that sensitive telemetry data isn’t being diverted to malicious third-party servers.
Implementing FDN on Cellular-Enabled Drone Accessories
Setting up Fixed Dialing Numbers requires a specific workflow that differs slightly from standard drone configuration. It involves a combination of carrier interaction and hardware settings within the drone’s control app (such as DJI Pilot 2, Autel Explorer, or QGroundControl).
Navigating the PIN2 Protocol
The first step in using FDN with drone accessories is obtaining the PIN2 code from the service provider. Many pilots confuse the PIN (Personal Identification Number) with the PIN2. While the standard PIN protects the SIM from unauthorized access upon startup, the PIN2 is specifically designed for accessing specialized services like FDN and call costs.
When configuring a drone controller, the pilot enters the cellular settings menu, selects the SIM card options, and locates “Fixed Dialing Numbers.” Upon clicking “Enable FDN,” the system will prompt for the PIN2. It is critical to note that entering the PIN2 incorrectly multiple times (usually three) will lock the FDN function, requiring a PUK2 (Personal Unlocking Key 2) to restore access. For large-scale drone operations, maintaining a secure database of these codes is a standard part of equipment logistics.
Configuration on Android-Based Smart Controllers
Because most modern professional drone controllers are Android-based, the process of adding numbers to the FDN list is straightforward but requires precision. In the context of drones, “numbers” in the FDN list often refer to specific service codes or short-codes used by the network to facilitate data-only connections.
- Access Settings: Navigate to the Android system settings of the smart controller.
- Network Setup: Go to ‘Mobile Network’ or ‘SIM card settings.’
- FDN List Management: Select ‘Fixed Dialing Numbers’ and then ‘FDN List.’
- Add Authorized Contacts: Here, the pilot adds the specific numbers or gateway codes provided by the drone manufacturer or the enterprise’s private network provider.
Once the list is active, the controller’s cellular radio will ignore any communication request that does not originate from or terminate at a destination on that list.
FDN and the Future of Beyond Visual Line of Sight (BVLOS) Operations
As the drone industry moves toward Beyond Visual Line of Sight (BVLOS) operations, the reliance on cellular accessories like 4G/5G dongles and integrated SATCOM/LTE modules will only increase. FDN is set to play a significant role in how these operations are regulated and secured.
Integrating FDN with Remote ID Requirements
Remote ID is now a mandatory requirement in many jurisdictions, requiring drones to broadcast their location, altitude, and pilot information. Some drones fulfill this via “Network Remote ID,” which sends data over cellular networks to a centralized tracking system. FDN ensures that the Remote ID module remains “locked” to the official tracking server. This prevents the drone from being “spoofed” or redirected to a fake server that could hide the drone’s position from aviation authorities.
The Intersection of 5G Modules and Access Control
The next generation of drone accessories will feature 5G modules capable of ultra-low latency and massive data throughput. With this increased power comes increased responsibility for data management. FDN, or its 5G equivalent in Network Slicing and Access Control, will be the cornerstone of ensuring that a high-speed drone connection isn’t hijacked for unintended purposes.
For creators using drones for aerial filmmaking, FDN allows the high-speed upload of 4K proxy files directly to a production server while blocking all other traffic. This ensures the maximum possible bandwidth is dedicated to the creative workflow, without interference from background apps or unauthorized users.
By understanding and utilizing Fixed Dialing Numbers, drone operators can transform a simple cellular accessory into a hardened, enterprise-grade communication tool. It provides the peace of mind that comes with knowing your drone’s “phone line” is open only to those it needs to talk to, ensuring every flight is secure, cost-effective, and compliant with the highest industry standards.