Morse Code Simulator: Send and Receive Between Two Stations

How to send a message with the simulator

1. Choose a connection at the top: Telegraph line (sounder clicks), Radio (600 Hz tone, optional static) or Ship lamp (silent light).
2. Press and hold the key at Station A, or hold the Space bar. A short press is a dot; hold about twice as long or more for a dash.
3. Pause three units to end a letter and seven to end a word; the decoded text and raw code appear at Station B as each letter closes.
4. Prefer typing? Enter up to 100 letters, numbers or Morse punctuation in Auto-send and select Send. SOS is sent as one continuous sign.
5. Stop keeps whatever reached Station B, Clear resets both stations, and Esc halts a transmission at any point.

Telegraph line, radio or ship lamp: three ways the signal travels

Each mode changes the receiver at Station B, the sound you hear and the things that can go wrong on the way. The line between the stations is slowed to 640 ms so you can follow the moving light; it is a teaching delay, not the physical speed of electricity.

The sounder and the tone are Web Audio approximations produced in the browser, not recordings of real instruments.

What happens between the key and the sounder

A telegraph key is a switch. Pressing the knob closes a circuit, a battery pushes current down the wire, and at the far station an electromagnet pulls the sounder arm down; releasing the key opens the circuit and the arm springs back. The operator never saw the current, only heard two clicks, and the time between them carried the code: a short closure was a dot, a closure three times as long was a dash.

The simulator shows the part that was invisible. A pulse of light moves along the line for each closure, the arm at Station B drops and returns in step with it, and the register tape underneath records each mark with the spaces that separate letters. Early recording instruments pressed those marks into a paper strip; the 1844 tape in the Library of Congress is one of them.

Sending speed: 10, 15 and 20 WPM

Speed is set in words per minute, with the standard word PARIS as the yardstick, and every timing in the simulator is derived from it: one unit equals 1200 divided by the WPM. The same unit decides whether your press counts as a dot or a dash, so the table below is also your dash threshold.

Start at 10 if your dashes keep decoding as dots; the longer unit gives you more hold time to commit. Move up only when a whole word decodes cleanly at the current speed.

Practice receiving with the receive challenge

1. Tick Receive challenge. The decoded line at Station B is hidden, but the sounder, lamp or tone and the register tape still work.
2. Type a word or short sentence in Auto-send, choose a speed, and select Send. Listen, or watch the tape, without looking at the raw code.
3. Type what you heard in the answer box and select Check. Each character is compared with the message that actually reached Station B.
4. Read the grade: it reports how many characters were correct, marks each miss with the expected letter, and flags extra characters at the end.

If the grade is low, drop to 10 WPM and send letters that are all dots or all dashes (E, T, I, M, S, O) before mixing them. In Radio mode, Stormy static removes marks on the way, so a wrong character there may be the line's fault rather than your ear's; the lost-marks counter tells you which.

Simulator, Telegraph or Tapper: which page do you need?

Three pages on this site put a key under your finger, and they do different jobs.

Use the Morse code simulator when you want the whole path from key to sounder, or while you are learning to copy by ear. Go to the Telegraph page for the older American code, and to the Tapper when the question is whether your dots and dashes are the right length. All three run in the browser on the same device.