Blinking or flashing Morse code uses any light source as the signal medium — a flashlight, a mirror, a phone screen, a signal lamp, or eye blinks. Short pulse equals dot. Long pulse equals dash. The ratios are the same as every other form of Morse code: a dash lasts three times as long as a dot.
Downed pilots have been rescued by flashing Morse with pocket mirrors. Sailors have contacted ships miles away with a single flashlight. In 1966, a US Navy officer communicated intelligence through controlled eye blinks during a televised captivity interview. Light-based Morse has real operational history.
Methods of Flashing Morse Code
Flashlight or torch: The most practical option. A short press is a dot; a long press (held for 3× the dot length) is a dash. Visible for miles in darkness and in daylight at shorter ranges. Cover the lens between cycles with your hand to create a clear pause between SOS repetitions.
Mirror or reflective surface: In direct sunlight, a mirror can be seen 10–15 miles away by aircraft and up to 7 miles by ships. Aim the reflection at the target and flash by alternately covering and uncovering it, or by tilting it in and out of the sun angle. This requires no battery and no equipment other than a reflective surface. Signal mirrors designed for survival kits have a sighting hole for accurate aiming.
Eye blinking: A short blink (under 0.5 seconds) is a dot. A held blink (1.5+ seconds) is a dash. Normal involuntary blinks serve as the intra-letter gap. This method requires an observer who knows to watch for it, and a receiver who knows Morse code. It is primarily useful in situations where the sender cannot move any other part of their body. Jeremiah Denton used it famously on North Vietnamese television in 1966 — you can read the full story in 10 Facts About Morse Code.
Phone screen: Turn the flashlight on and off, or use an app that flashes the screen. A phone held against glass is visible from outside a building. Useful in situations where you cannot get outside to signal.
Vehicle headlights or hazard lights: Three short flashes, three long, three short. Other drivers or observers nearby may recognise SOS. Range depends on visibility conditions.
Timing When Flashing
The ratios are identical to tapped and transmitted Morse: dot = 1 unit, dash = 3 units, intra-letter gap = 1 unit, letter gap = 3 units, word gap = 7 units.
For emergency SOS signalling, you do not need to think about precise timing — the three-three-three pattern is forgiving of minor timing variations. What matters is that your dashes are clearly longer than your dots and that there is a clear pause between SOS cycles.
For communication rather than just distress signalling, timing precision matters. A receiver trying to decode a full message will struggle with inconsistent timing. Practise until your dot/dash ratio is consistent and your letter gaps are clearly longer than your intra-letter gaps.
How to Flash SOS Step by Step
Using a flashlight:
- Three short flashes (dot duration — about half a second)
- Three long flashes (dash duration — hold for 1.5 seconds each)
- Three short flashes (same as step 1)
- Cover the lens completely — pause for 3 seconds
- Repeat from step 1
Continue repeating until you see a response, hear a response, or are certain the signal has been received. Do not stop after one cycle — receivers may need several repetitions to recognise the pattern and determine your location.
At night, add directional movement: after the SOS cycle, sweep the flashlight in a slow arc in the direction of potential rescuers. The movement helps them determine your position relative to theirs.
Famous Blink Morse Moments
The most documented case of eye-blink Morse is US Navy Commander Jeremiah Denton in 1966. Forced onto North Vietnamese television for a propaganda interview, Denton blinked the word TORTURE while appearing to answer questions calmly. His captors did not notice. American naval intelligence analysts watching the footage decoded it. It was the first direct confirmation of prisoner mistreatment from inside North Vietnam.
In 2005, a group of hikers stranded in Washington State were rescued after spelling SOS in the snow using pine branches. A search aircraft spotted the pattern and directed ground teams to their location. The combination of a ground signal and eventual radio contact saved them.
The Titanic's radio operator Jack Phillips transmitted SOS continuously by wireless Morse until power failed — roughly 15 minutes before the ship sank. The Carpathia received it and rescued 705 survivors. The full story is in The History of Morse Code.
Practising Light Morse
To build reliable light signalling speed, practise the same way you would any Morse — by audio first. Use the Translator to hear SOS and common letters until the patterns are automatic. Then transfer that timing to your flashlight hand.
The Practice mode builds the same timing instincts needed for flashing — Two-Button mode is essentially flashing Morse in software form. The timing you develop there transfers directly to a physical flashlight.
Once SOS is automatic, learn the individual letters S (···) and O (———) through the Learn page lessons. These two letters, plus the ability to combine them into the SOS prosign, are the most critical light signalling skills for emergency preparedness.
Light Signals and Aviation SAR
Search and rescue aircraft actively look for light signals from people in distress. Standard SAR protocol in many countries includes sweeping for rhythmic flashing patterns — and the three-three-three SOS pattern is specifically what operators are trained to notice.
The most effective light signalling combination is: a signal mirror (for long-range daytime visibility) plus a flashlight (for after dark) plus a ground signal (rocks or debris spelling SOS for aerial recognition when active signalling is not possible). The redundancy increases rescue probability significantly.
International SAR agreements require aircraft to dip their wings twice in acknowledgement when they have spotted a distress signal from the ground. If you see a low-pass followed by two wing dips, you have been seen — stop active signalling and prepare for pickup or further contact.
Practising Light Morse for Real Proficiency
The difference between knowing the SOS pattern and being able to execute it correctly under stress is practice. Muscle memory under pressure comes only from repetition.
A useful exercise: practise sending SOS with a flashlight in a dark room until you can do it accurately without counting signals. Time it — SOS at 5 WPM (the minimum for recognition) takes about 8 seconds per cycle. At 10 WPM, 4 seconds. Your goal is to send one cycle in under 6 seconds reliably.
Then add other letters. E (one short flash), T (one long flash), and A (short-long) are all easily practised with a flashlight. Once you can flash all three without hesitation, add S (three short), O (three long), and you have the six letters that cover the most critical communication patterns. Use the Learn page audio lessons to build the patterns, then transfer them to flashlight practice.
Eye-Tracking Morse Input Technology
Modern eye-tracking cameras combined with dwell-time detection have made eye-blink Morse input a practical communication method for people with locked-in syndrome and other severe paralysis. The technology works by detecting the duration of an eye closure — a brief blink registers as a dot, a held closure as a dash.
Commercial systems like Tobii Dynavox and open-source alternatives like OptiKey implement this. Typing speeds of 5–10 WPM are achievable with practice — slow compared to voice, but for someone who cannot produce any other controlled output, it represents full linguistic communication.
The same Morse code taught in the Learn page lessons is what these users learn. The patterns are identical. The delivery mechanism is different. The code itself is the same 190-year-old system.
The Mirror Signal — A Detailed Guide
A signal mirror is arguably the most underrated survival tool. In direct sunlight, a properly aimed mirror can be seen from aircraft at altitudes up to 15,000 feet and from ships at distances of 7–10 nautical miles. It requires no battery, no maintenance, and creates a signal that is physically impossible for cloud or atmospheric noise to obscure.
Technique: hold the mirror facing the sun, extend your other hand at arm's length, and create a "V" with your fingers around the target. The sunlight reflected from the mirror should pass through this V when aimed correctly. Alternate covering and uncovering the mirror to create dot and dash patterns. Short cover = dot, long cover = dash.
Practise this in the garden before you need it in the field. The aiming technique takes practice to execute reliably. A military-spec signal mirror with a sighting hole simplifies the aiming significantly and is inexpensive enough to include in any emergency kit.
Practising Light Morse Without Equipment
You do not need a flashlight to practise light Morse timing. Any controlled on-off signal works: covering and uncovering a light source with your hand, opening and closing an application window on a screen, tapping a table with a pen (short tap = short cover = dot, held = long cover = dash).
The timing practice transfers completely between these methods. What you are building is the internal sense of dot-length, dash-length, and the gaps between signals. Once that timing is accurate in one context, it transfers to all others. Ten minutes of hand-over-flashlight practice in a dark room builds the same skill as ten minutes of Two-Button tapping in the Practice mode.
For the HELLO post complement: knowing HELLO in Morse means you can flash it to someone who knows Morse — a simple greeting that doubles as a demonstration of the skill. H (four short flashes), E (one short), L (short-long-short-short), L again, O (three long). This 13-signal word is a complete, meaningful message that takes about 5 seconds to flash at slow speed.
Build your flashlight vocabulary starting with SOS, then HELLO, then the core letters from the Learn page lessons. With 12 letters you can spell most common English words. With 26 you can communicate any message, including coordinates, names, and situation reports, to any receiver with Morse knowledge worldwide.