The morse code chart

Every letter, digit, punctuation mark and prosign, read from the same table the translator uses.

The alphabet is ordered by how common the letter is

E is a single dit and T a single dah because they are the two most frequent letters in English; Q and Y are four symbols each because they are rare. Morse was compressed by letter frequency almost a century before anyone wrote down the theory of why that works.

Numbers are all five symbols long

Every digit is exactly five marks, running from ----- for zero to ----. for nine, with the balance of dots and dashes shifting one place at a time. That regularity makes digits far easier to learn than letters, and it is why callsigns and signal reports are read digit by digit.

Prosigns are one symbol, and some are ambiguous

A prosign is two or three letters sent with no gap between them, so <SK> is one symbol rather than two letters. Several share a code with a punctuation mark — <BT> and the equals sign are both -...-, <AR> and plus are both .-.-. — and nothing in the signal separates them. Only what the message is doing tells you which was meant.

SOS is not three letters

It is a single unbroken symbol, ...---..., with no gaps inside it. Sent as three separate letters it is still readable but it is no longer the distress call, which is defined precisely by the absence of those gaps.

Questions

What is SOS in morse code?

Three dots, three dashes, three dots — ... --- ... — and it is sent as ONE symbol with no gaps between the letters, which is why it is written <SOS> rather than S O S. It was chosen because it is unmistakable and easy to send, not because it stands for anything; "save our souls" was invented afterwards.

What are prosigns?

Procedural signals: two or three letters run together as one symbol with no gap between them, written like <SK> for end of contact or <BT> for a pause. Some share a code with a punctuation mark — <BT> and the equals sign are both -...- — and only context tells them apart.

Why do some characters come back missing?

Because morse has no code for them. There is no standard morse for an accented letter, a curly apostrophe or an emoji, so anything without a code cannot be sent. This site lists exactly what it had to drop rather than quietly leaving it out, which is what most translators do.