In days of yore when telegraphs were the means of long distance electronic communication, how did a telegraph operator in, say Boston, know he was sending to Philadelphia? Was there something like a call sign that a telegraph operator in Philadelphia was assigned, and when he heard it he knew the message was for him?
But in that case, were they party lines? How would you separate your dots and dashes from all the others?
I suppose the main question is, how did all that work?
The operator waited for a break in traffic (the dots and dashes) and sent out a I am going to send message. If no objections He would begin sending starting with which office it was addressed to.
Can you imagine? People taking turns with the sole means of communicating with the outside world?
It is my understanding that in WWII experienced and skilled decoders could recognize the sender, either enemy of friendly, depending on the individual senders special quirks.
There is a broader question here, I think. In pre-wireless days, how were messages routed? If you were siting in an office in Boston with, presumably, one wire leaving the building, how did you make sure that your message went to, say, New York, rather than Philadelphia? Were there exchanges, like the early telephone exchanges, with operators and plugboards, that you had to contact, before sending your real message, with a request to be appropriately routed? If not, what?
stations had identifiers.
when you were on the same line then you time shared.
when there were multiple line then you were routed.
In other words, can you imagine people not expecting a natural entitlement to instant gratification.
Any idea how common multiple lines were? Would you have a telegraph office in New York, say, with multiple lines to Boston, Philadelphia, and Albany, each connected to a different telegraph set inside the office?
I would think you must, otherwise how many messages could you really send/receive in a day on one line?
Devices for sending multiple messages on one line started being developed in the 1870s; Edison had many patents for various methods of using two, four, and eight messages on the same line. IIRC, Alexander Graham Bell was working on that when he invented the telephone.
This article on the Morse repeater is very interesting. The first main telegraph line was between Baltimore and Washington. That’s where the technology was refined and proven in a day to day working environment.
I’m surprised they even managed 300 miles on those early wires. They needed people to receive and repeat the message as it went cross country. Morse developed the first repeaters.
http://www.telegraphlore.com/instruments/athearnrptr/prescott.htm
And relaying a telegraphic message was apparently how relays got their name. Fascinating, from a nerdish standpoint.
what relays would be called a relay.
for the nonnerd (not clicking on the link) a relay, as mentioned, is an electronic device that is an electromechanical switch which can be used in many ways.
Remember, telegraphs weren’t consumer goods. Or typical small business goods. They were the then-equivalent of FedEx; a quick but not instant way to deliver information compared to all the alternatives.
You went to an office, wrote your message on a paper form, paid the person behind the counter, and they gave the form to somebody in back who spent all day Morse-ing to other professionals in other offices in other cities. Eventually your message got to the top of the pile & was transmitted. That might have been minutes or hours later.
A professional at the other end heard it and copied it onto another form which was given to somebody else to physically deliver to the recipient’s home or office.
“Instant gratification” and people taking turns had nothing to do with it.
And yes, not too long after telegraph became common large businesses built dedicated services just for their internal use. Or at least contracted with the wire carriers for dedicated telegraph stations in their major offices.
The rest of the story up through Twitter is simply improving the speed and scale while reducing the number of human-in-the-loop processes.
LSL Guy gave great explanation.
He does something a lot like the operators back then did & does it a lot.
He listens to a lot of stuff on frequency in his sector that the ATC controller is saying and notices when it is him they want to do somethng.
It would seem amazing to many that he will respond to his call sign out of all the busy chatter. ( He actually will also pick up stuff up that might cause him trouble in the future even if he was not called because he knows where he is, where he is going, and when he’ll get there, but that is a whole nuther thread. )
The telegraph operators were a lot like that, they each had a unique call sign and they would pick up on it ( hear it ) among all the clicking that would just be noise to me. It was a party line and everyone is listening in, but the one guy wrote the message down for the Mayor of his town or whoever that it was intended for. The rest just eavesdropped.
Long distance messages were relayed a lot of the time from region to region just like planes are handed off to different ATC sectors as they go across the country.
YMMV 
If the OP is really interested in this subject, he should get the book “The Victorian Internet”, a very readable and in-depth look at the development of the telegraph. I don’t have the author’s name, but the title is unique enough that it should be easily found.
I also recommend Neal Stephenson’s massively long article on undersea cables that he did for Wired (appropriately enough):
Remember jokes about people not knowing how to use computers? Like the cupholder joke? There were jokes about people not knowing how to use the telegraph. Like the lady who gave the telegraph man a sealed envelope and snatched it back, indignant, when he started to open it. That was a personal message - how dare he read it!
As I understood it, there were “lines”, with a number of operators on each line listening in for something addressed to them. One thing I recall reading implied these lines tended to follow railroad lines - since the right of way was established to pull the wire, and the individual stations were also convenient telegraph offices.
I don’t know about long distance- i.e. Boston to Philadelphia, but I presume there would be a relay via a terminus in, say, New York. One can imagine a spoke-and-hub arrangement where longer distance telegrams would bounce along the long distance lines then to the appropriate local distribution line to the local town’s telegraph office.
IIRC, the “I am going to send” message waited for a acknowledgement reply from the operator at the receiving end, so a message didn’t get lost during washroom breaks. Theoretically, messages tended to be short so there always should be an opportunity to jump in.
To add to the above, major sites had multiple lines, and operators would use plugs in a switchboard to connect with another operator. There were generally fixed times for individual operators to handle the expected traffic, although there were also dedicated interoffice “pony lines” that were used for coordinating operations between sites. Routing would be handled by time schedules and set policies for transfers, which often required resending the message down another line. Operators would also have fare schedules so they would know how much to charge for various destinations.
Many railroad lines would only have a single telegraph line for all traffic, primarily to handle railroad operations, but also for commercial and private telegrams. This was set up as a party line–each station would have a sounder that made all the telegraph line’s traffic audible in all the stations, which all station operators were responsible to monitor. (It was considered bad practice if you tried to transmit anything other than an emergency message when someone else was sending). Each station had a unique callsign, so you could get their attention just by including their call at the start. Operators also had individual “sines” if you wanted to get the attention of a specific persons. A skilled operator could listen to the traffic while doing paper work, note anything being sent to their office, then write down the full message after it was completed.