You bought a Radiomaster TX16S or Boxer, flew the default setup for months, and now you want more than basic channel mixing. The answer is in EdgeTX’s logical switches and special functions — a deceptively simple system that can automate everything from pre-arm voice prompts to dynamic rate switching based on battery voltage. Here is how to build configurations that make your radio work for you, not the other way around.
EdgeTX Logical Switches: The Building Block You Are Not Using Enough
A logical switch is exactly what it sounds like: a virtual switch that activates when a condition is true. The magic is that logical switches can reference other logical switches, creating chains of logic that go far beyond simple switch assignments.
Step 1: Create a Pre-Arm Safety Chain
The most practical first project is a pre-arm check that prevents arming unless multiple conditions are satisfied. This eliminates the “throttle up while carrying the quad” accident that every pilot has done at least once.
- Go to the Logical Switches page (MDL → Logical Switches on touchscreen, or the LSW tab on the model page)
- Create L01:
a<x, Thr, -95— true when throttle stick is fully down - Create L02:
AND, L01, SF↓— true when throttle is down AND switch SF is in the down position - Create L03:
Sticky, SA↓, SA↑— a sticky switch that latches on when SA is pulled down and unlatches when SA is pushed up
Now L02 is your pre-arm condition (throttle down + arm switch down). Use L02 as the source for your actual arm channel in the Mixer page instead of a raw switch.
What this gives you: even if you bump the arm switch walking back to the pits, the quad will not arm unless the throttle is fully down. Add more conditions to L02 (like a momentary button press) for a two-stage arm that requires deliberate action.
Step 2: Build a Dynamic Rate Profile Based on Flight Mode
Most pilots fly one rate for everything. The better pilots I know switch between a “precision” rate for tight proximity and a “freestyle” rate for open air — automatically, based on which flight mode they are in.
- Create L04:
AND, SB↓, SB↑— true when switch SB is in the middle position (your “precision” mode) - Create L05:
AND, SB↓, SC↓— true when switch SB is down AND SC is down (your “freestyle” mode) - In the Mixer page, create duplicate lines for Aileron, Elevator, and Rudder:
– Line 1: weight 80%, switch L04 (precision rates)
– Line 2: weight 100%, switch L05 (freestyle rates) - Add a third “catch-all” line with switch
!L04AND!L05for default rates
Now when you flip SB to the middle position, your stick rates scale to 80% — tighter control for threading gaps. Flip SB down and you get full rates for freestyle. No menu diving required.
Step 3: Voice Callouts That Actually Help
EdgeTX can speak telemetry values and flight mode names, but most pilots set up callouts that are more annoying than useful. The trick is to make callouts trigger on events, not timers.
- In Special Functions, create SF1:
L01, Play Value, RxBt, repeat 10s— reads receiver battery voltage every 10 seconds, but only when the throttle is down (L01 is your “throttle low” logic switch from Step 1). Otherwise the voice fights with your spotter and you tune it out. - Create SF2:
L04, Play Track, "precision mode"— announces mode change when you switch - Create SF3:
L05, Play Track, "freestyle mode" - Create SF4:
Telemetry, RxBt, <, 5.0V, Play Track, "low battery", repeat 30s— only triggers when receiver battery actually drops below 5V
The repeat interval keeps you informed without the constant chatter that makes you mute the radio speaker.
EdgeTX Logical Switch Parameter Reference
| Function | What It Does | Real-World Use | Gotcha |
|---|---|---|---|
| a<x | True when value is below threshold | Throttle position safety (a<x, Thr, -95) | Stick must be calibrated for -100/+100 range |
| a>x | True when value exceeds threshold | Altitude warning (a>x, Alt, 120) | Sensor must be discovered and active |
| AND | True when all conditions are true | Multi-condition pre-arm | Max 3 inputs per AND switch; chain for more |
| OR | True when any condition is true | Any-of-multiple trigger conditions | Easier to trigger than intended if not careful |
| Sticky | Latches on first edge, unlatches on second | Toggle behavior from momentary switches | Remains latched across power cycles |
| Edge | Brief pulse on transition | One-shot triggers, camera shutter | Pulse duration in 10ms units — keep it fast |
| Timer | True for a set duration after trigger | Delayed actions, timeouts | Timer resets if trigger condition remains true |
| Delta | True when value changes faster than threshold | Rate-of-change detection (e.g., speed warning) | Threshold is in raw telemetry units per 10ms |
Special Functions That Most Pilots Miss
EdgeTX special functions can do more than play sounds. Here are setups I use on every model:
- Override CH5 (Arm) when radio is not transmitting: Special Function →
!L02, Override CH5, -100, enabled. This forces the arm channel to the disarmed position whenever the pre-arm conditions are not met. If your quad’s failsafe somehow leaves the arm channel high, this catches it. - Backlight on telemetry warning:
Telemetry, RQly, <, 50, Backlight. When link quality drops below 50%, the screen flashes — visible in peripheral vision while wearing goggles. - Trainer mode on momentary button:
SH↓, Trainer, enabled. Hold the shoulder button to give control to a student/buddy box. Release to take back control instantly. No menu toggle needed.
What Pilots Get Wrong with EdgeTX Programming
Mistake 1: Creating logic chains that depend on switch positions that can never happen simultaneously. If L01 requires SB↓ and L02 requires SB↑, an AND of L01 and L02 will never be true. Test each logic switch individually using EdgeTX Companion’s simulator before loading onto the radio.
Mistake 2: Using “Play Track” with too-short repeat intervals. A 5-second repeat on a voltage callout means you hear “four point two volts” twelve times per minute. Unless your pack depletes in 60 seconds, that’s noise. Use 15-30 second repeats for telemetry and event-driven callouts for mode changes.
Mistake 3: Forgetting that EdgeTX mixer lines are processed top to bottom. The first active line that a switch condition matches wins. If your “precision” line (weight 80%) is below a “default” line (weight 100%) in the mixer, the default line always activates and your precision line never runs. Order matters.
Mistake 4: Copying a model setup and forgetting to re-bind. EdgeTX copies all logic, mixes, and outputs. But the receiver binding is stored on the RF module, not in the model file. A copied model’s channel outputs will go to the old receiver unless you re-bind or change the receiver number.
Mistake 5: Enabling “Global Functions” that conflict with model-specific functions. Global functions run on every model. If you set a global throttle cut that activates on SF↓, and model 3 uses SF↓ for a camera trigger, both functions fire. Check Global Functions when debugging unexplained radio behavior.
⚠️ Regulatory Notice: The radio programming techniques in this article should be used in accordance with the latest 2026 drone regulations in your country or region. Always verify local laws regarding control link frequencies, transmission power limits, and failsafe requirements. Regulations vary significantly between the FAA (US), EASA (EU), CAA (UK), CAAC (China), and other authorities.
Related Guides
Your radio is only half the link. Our Crossfire Nano RX binding guide covers the receiver side of a solid control link. For setting up the flight modes these logic switches are selecting, see our Betaflight Modes and Aux Switch Configuration guide.
Radio Hardware Pick
All of these EdgeTX features work on any EdgeTX-compatible radio, but the big color touchscreen on the uavmodel Radiomaster TX16S Mark II MAX makes navigating logical switches and special functions dramatically easier than scrolling through a monochrome screen. It ships with EdgeTX pre-installed, has hall-effect gimbals, and includes a CNC aluminum faceplate.