Very confused by this description of how early Morse code & telegraphs worked - Please help clarify

Factual Questions
1

In this Slate article about the history of keyboards there is this section quoted below.

So… you have this “rotator” that cues each individual telegraph operator to send a single letter when prompted by a clicking noise.

A few questions -

How does this “rotator” work?

Are these operators all in the same room or in separate locations ?

How is the message reconstructed at the receiving end if the rotator is breaking up the time slot intervals for sending?

2

don’t have actual cite but

if you had a single telegraph wire between two cities with 5 transmitting operators on one end and 5 receiving operators on the other end. an automatic switch would switch between each every second and each end is synchronized. with the Baudot code all letters/numbers take the same length of time not dependent on the quality and speed of a Morse code operator. each operator would would send a character when the rotor indicator would indicate it being their turn.

so each operator would send on their turn (time enough to place fingers on 5 key positions) and the receiver would sequentially accumulate the letters.

3

The article is describing (poorly) what we would now call a time-division multiplexer. The idea is, instead of running five different telegraph lines between two towns, you can run a single line and send five signals over it, by giving each signal a brief period of time during which to send. The five operators in question would be in different places in one town, with all their lines coming together at a single place to be multiplexed and sent down a long-distance line to another town (or wherever.)

A receiver at the other end of the long-distance line, which is synchronized, demultiplexes the fix signals and sends them down separate wires to their destinations.

The actual mechanics of the multiplexing and demultiplexing were handled by complicated clockwork/relay devices invented by Baudot.

4

I think all 5 operators are sending separate, different messages. The Baudot system is a way in which you can send 5 messages simultaneously over a single line.

With a Morse system you could only send one message over the line at a time, so you had to wait until the first message was sent until you could send the second. The line itself is capable of carrying a much higher rate of information, so you could, in principle, have sped things up by making the individual dots and dashes shorter, but a human operator could only send so fast (and the receiver at the other end could only decode so fast) so you could not really do that, and the lines were not being used to their full capacity. The Baudot system used the line much more efficiently by sending 5 messages simultaneously over the same line, the operators, in effect, taking turns to send each letter of their message.

I would presume that the operators would normally all have been in the same room, but perhaps that wasn’t entirely necessary.

5

Exactly. Digital CODECS do the same thing. Except about a quadrillion times faster.

6

So how were the two ends synchronized? Was there a second line that carried some sort of synchronization signal?

Was synchronization even necessary? Can’t the receiver just have 5 pieces of paper, write down the first letter on paper 1, the second letter on paper 2, and so on through the 5th, which is written on paper 5. Then you start over with 1 again.

7

With a scheme like that, the Teletype was an invention just waiting to happen.

8

Unfortunately I don’t recall how the two ends were synchronized; it might have involved an out-of-band signal or some kind of control signal on the line.

There’s no person at the receiver. The other end is just a demultiplexer which splits the signal into five separate streams to sends them to their destinations. The whole point of the invention is that the multiplexing and demultiplexing is automatic, to make it practical to build long telegraph lines that can handle more than one signal at a time.



 signals  +-+                         +-+
A-------->| |                         |d|-------->
B-------->|m|                         |e|-------->
C-------->|u|------------------------>|m|-------->
D-------->|x|                         |u|-------->
E-------->| |                         |x|-------->
          +-+                         +-+

That’s why teletypes used (a form of) Baudot code. And that’s where the baud unit comes from. (Remember those?)