Some brand names become the de facto name for the generic product. Xerox, for example. Or Velcro. Teletype was a trademark, but it has come to mean just about any teleprinter communicating with another teleprinter or a computer. The actual trademark belonged to The Teletype Corporation, part of Western Electric, which was, of course, part of AT&T. But there were many other companies that made teleprinters, some of which were very influential.

The teleprinter predates the computer by quite a bit. The original impetus for their development was to reduce the need for skilled telegraph operators. In addition, they found use as crude wordprocessors, although that term wouldn’t be used for quite some time.

Telegraph

Early communication was done by making and breaking a circuit at one station to signal a buzzer or other device at a distant station. Using dots and dashes, you could efficiently send messages, but only if you were proficient at sending and receiving Morse code. Sometimes, instead of a buzzer, the receiving device would make marks on a paper — sort of like a strip recorder.

In the mid-1800s, several attempts were made to make machines that could print characters remotely. There were various schemes, but the general idea was to move a print head remotely and strike it against carbon paper to leave a letter on a blank page.

By 1874, the Frenchman Èmile Baudot created a 5-bit code to represent characters over a teleprinter line. Like some earlier systems, the code used two shift characters to select uppercase letters (LTRS) and figures (FIGS). This lets the 32 possible codes represent 26 letters, 10 digits, and a few punctuation marks. However, if the receiver missed a shift character, the message would garble badly. This was especially a problem over radio links.

Paper Tape

Donald Murray made a big improvement in 1901. Instead of directly sending characters from a keyboard to the wire, his apparatus let the operator punch a paper tape. Then a machine used the paper tape to send characters to the remote station which would punch an identical tape. That tape could go through another machine to print out the text on it. Murray rearranged the Baudot code slightly, adding things we use today, like the carriage return and the line feed.

The problem that remained was keeping the two ends of the circuit in sync. An engineer working for the Morton Salt Company solved that problem, which Edward Klienschmitt independently improved. The basic idea had been around for a while — using a start pulse to kick off each character — but these two patents around 1919 made it work.

Patents

Instead of fighting a big patent war, the two companies, Morkrum (partly owned by the owner of Morton Salt) and Klienschmitt, merged in 1924 and produced an even better machine. This was the birth of the modern teleprinter. In fact, the company that was formed from this merger would eventually become The Teletype Corporation and was bought by AT&T in 1930 for $30 million in stock.

Some early teleprinters were page printers that typed on the page like a typewriter. Others were tape printers that spit out a tape with letters on it. Often, the tape had a gummed back so the operator could cut it into strips and stick it to a telegram form, something you may have seen in old movies.

In addition to public telegrams, there were networks of commercial stations known as Telex and TWX — precursors to modern e-mail. These networks were like a phone system for teleprinters. You’d dial a Telex number and send a message to that machine. Many teleprinters had an internal wheel that a technician could set (by breaking off tabs) to send a WRU code (who are you) in response to a query. So connecting to the Hackaday Telex and sending WRU might reply “HACKDAY.” In addition, you could ring a bell on the remote machine. So a single bell might be a normal message, but ten bells might indicate an urgent message.

Word Processing

While replacing telegraphs was an obvious use of teleprinter technology, you might wonder how people could use these as crude word processors. The key was the paper tape and a simple paper tape trick. A Baudot machine would have five possible punches on one row of the tape. You can think of it as a binary number from 00000 (no punch) to 11111 (all positions punched out). The trick is that if all positions are punched out, the reader would ignore that position and move on to the next character. They also usually had a code that would stop the reading process.

This allowed you to do a few things. First, you could punch a tape and then make many copies of the same document. If you made a mistake, you could overpunch the tape to remove any unpunched holes and “delete” characters. It was also common to use several fully punched-out characters as a leader or a trailer, which allowed you to line up two tapes and paste them together.

So, to insert something, you could identify about a dozen characters around the insert and over-punch them. Then, you’d prepare another tape that had the new text, including the characters you punched over. You’d start that tape with a leader and end it with a trailer of fully punched positions. Then, you can cut the old tape and splice the new tape’s leader and trailer over the parts you punched out in the first step. A lot of work? Yes, but it’s way better than retyping everything by hand.

Once you create your master tape, you could turn out many originals. You could even do a sort of mail merge. Suppose I have a form letter reminding you to pay your bill. The master tape would have a pause in key places. So, the operator would do something like type the date, name, and address. Then, they would press start. The tape would type “Dear ” and then read a stop code. The operator could type the name and press start again. Now, the tape would run up until a later point, and another stop code would let the operator enter the account number and press start again. The next stop might be for the balance due, and a final stop for the due date. Pretty revolutionary for the 1940s.

Really high-tech installations used two tapes, one loop with the form letter and another unlooped tape with the input data. The operator did almost nothing, and all the letters were printed automatically.

Of course, not all teleprinters were used like this. Many teletypes had letters in their name to indicate their configuration. An RO, for example, had no keyboard or paper tape. KSR teletypes (e.g., KSR 28) had keyboards and no tape equipment. An ASR (like an ASR 33) had both keyboards and a paper tape reader and writer). These ASR 33s were especially popular as I/O devices for early microcomputers. Teleprinters were also used on many early computers. Both the Harvard Mark I and the MIT Whirlwind I used Frieden Flexowriters, a teleprinter made by Frieden, a company eventually acquired by the Singer sewing machine company.

Flexowriters were known to be used to generate form letters for both the White House and the United States Congress. Combined with an autopen, the system could create letters that people would perceive as hand-typed and signed, even though they were really automatically generated. You can see a Flexowriter in action in the video below.

Handwriting Computer

Another trick was to take a tape with a header and a trailer and paste them together to form a loop. Then the printer would just print the same thing over and over. I saw a particularly odd use of this back in the 1970s.

I was in a mall. There was a booth there purporting to have a handwriting analysis computer. I wasn’t willing to spend $2 on an obvious scam, but I hovered around, trying to understand how it worked. It was oddly familiar, but I couldn’t place it. The machine was very large and had many blinking lights and spinning disks. It looked like a prop from a very cheap 1950s science fiction movie.

People would pay their money and write something on a piece of blank paper. The clerk would take that paper and place it in a slot. With the press of a button, the machine would suck the paper in and spit it out with some fortune cookie message towards the bottom of the page. It might say, “You are stronger than people realize.”

After a half hour, I remembered where I recognized the machine from. The big box was, of course, a fraud. But it was hiding something and the only part of that something visible was a row of brown buttons. Those brown buttons belonged to a Frieden Flexowriter. You can see the brown buttons near the top of the unit in the picture.

Once I realized that was the “brain” of the device, it was obvious how it worked. Hidden inside was the paper tape reader. It had a loop of tape containing some line feeds, a fortune, more line feeds, and a stop code. The whole loop might have had a dozen or so fortune cookies, each with a stop code at the end of each.

When you put the paper in the slot, it really went around the teleprinter’s platen. You press the start tape button, and the line feeds suck up the paper and advance past the writing. Then, the fortune types out on the page. The final line feeds eject the page, and then it stops, ready for the next fortune. Pretty clever, although totally fraudulent.

Death of the Teleprinter

Teleprinters couldn’t survive the “glass teletype” revolution. CRT-based terminals swept away the machines from most applications. Real wordprocessors and magnetic media wiped out the applications in wordprocessing and typesetting.

Companies like Teletype, Olivetti, and Siemens (disclosure: Hackaday is part of Supply Frame, which is part of Siemens) stopped making teleprinters֫. In today’s world, these seem impossibly old-fashioned. But in 1932, they were revolutionary, as seen in the video below.

If you noticed the similarity between most modern teleprinters and electric typewriters, you aren’t wrong. Linux will still let you log in using a hardcopy terminal.