Below is a fantastic write-up on telegraphy for beginners from a member of the “slowspeedwire” mailing list:

Telegrams are the original email. They were all addressed to a specific individual. Now there were “book” telegrams, basically the spam of their day, the same text sent to a number of individuals, but each copy still each needed an individual address. Telegrams were originally hand delivered by a messenger service. They could also be picked up by a messenger. Businesses that had a modest volume of telegram requirements would have a WU (or Postal Telegraph) “call box” installed (see: youtube.com/watch?v=KdVlKgYwAyc for a demonstration of one, however the narrator refers to the “electronics” in the box. There is no such thing, it is just a mechanical spring which causes a contact arm to follow a code wheel which would send a unique 2 or 3 digit pattern on the wire, but not Morse Code). This would be connected to the nearest WU office (in big cities there would be one of these at least every 10 blocks) and cause the messenger to come to your address, usually riding a bicycle).

However, when telephones started to become common, WU would just call the addressee and read them the telegram. If you wanted hard copy delivery they would either put it in the mails or you could pay extra to have it hand delivered. About a dozen years ago shortly before WU’s telegram service was finally ended, I once asked what it would cost to have a telegram delivered and was told about $18. By then, however, WU was only handling about 20,000 telegrams a year which is why they shut down the service. Even sending a telegram became quite expensive even if it was just phoned to the recipient. Email had taken over the business. And of course, WU’s telegram service was by then handled just like email anyway. Why pay to have someone call a message to your desired recipient when you could do it yourself, or of course just send an email?

All that said for about 80 years, up until the early 1950’s, if you had a business in a large city, say NYC or Toronto and had a question for another business say in Chicago, you could twist the knob on your call box and within a few minutes a messenger would appear at your door to take your message. It would likely be delivered by a messenger to the recipient in Chicago by another messenger within an hour or so and he would wait for the recipient to write out his reply, take it back to his local office and you might very well have his response, once again delivered by a messenger, in your hand in under three hours from when you first twisted the knob on your call box. It was once said (by a famous WU president) that the value of the telegraph was not that it was faster than the mails but that it in fact “annihilated time”. After the early 1950’s if you had a telegram to send you would call the local WU office on your phone and read the WU operator your message and your desired recipient would be called with it and asked for a response. Of course by the early 1950’s most telegram business was handled by teletype equipment, not Morse operators at their keys, although WU didn’t shut down the last of their Morse ops until the mid 1960’s.

I’ve been on the Internet now for about 25 years but was actually working for Carnegie Mellon University’s computer science department when their ARPANET IMP was delivered and installed in 1970/71 while finishing up my electrical engineering degree and briefly used the ARPANET to access other university computer systems (Stanford IIRC) until I graduated and went out into the “real world”. If you are really interested in how things were back in the “dark ages” here’s a link to a web page with several downloadable autobiographical documents about my “early daze”: has-been4.ddns.net:8080/wp2/index.php/?p=15045

If you want to hear American Morse these days, short of having someone record an audio file for you, you really need to download and install MorseKOB. (There’s also a receive only program, Morse News, but it also needs to be downloaded and installed.) There is a web version available, MorseKOB 3.0, which is written in Java but due to issues with Java not all platforms will let you run it anymore, but it doesn’t really require a download to your computer. If you can run it, you may still not be able to connect real instruments to it, only hear the clicks in your computer sound system. In any case you will likely have to override security protections in your computer to use the web version.

The regular version of MorseKOB can be used to record an audio file. I’ve attached an .mp3 (sorry about the album cover) of a short sequence of a news item from wire 109 (old folks shouldn’t take aspirin) and one simulated railroad OS report from wire 113 done this way for your amusement. — Chris Hausler

Note: To listen to the recording mentioned above, please look in our NPSTN/C*NET directory and find the number associated with this recording, which you can dial directly from either NPSTN or C*NET or indirectly from one of the PSTN inbounds listed on the home page.

Below is a great explanation of how a spark transmitter works:

Perhaps the easiest way to explain how a spark transmitter works is as follows:

An AC wave form (or DC via an interrupter) is applied to the primary of a high voltage transformer. This is switched on and off via a telegraph key. When keyed, a high voltage at the transformer output is applied to a simple L-C resonant circuit in which a spark gap is present. This excites the L-C circuit (coil and condenser), which rings at its resonant frequency. This L-C tuned circuit is then coupled into an antenna system, either directly or via a matching network called an “oscillation transformer.”

A spark transmitter produces a “damped oscillation.” An analogy to a damped oscillation might be that of “ringing a bell.” Each time the striker hits the bell, the bell rings at its resonant frequency. The mass of the bell damps the oscillation. That is, the amplitude (loudness) of the oscillation decreases with time. Undoubtedly, you’ve tapped a bell, a glass, a tuning fork, or other object that “rings” with decreasing volume (amplitude) until it dies out. In the case of a spark transmitter, each discharge across the gap rings the “bell,” or “L-C” resonant circuit. In between excitation, the resonant circuit “rings” in the form of the aforementioned “damped oscillation.”

The term “continuous wave” is in actuality a term that differentiates the undamped oscillation generated by an HF alternator or vacuum tube transmitter from its predecessor spark technology. In a CW transmitter, the oscillation is undamped and the unmodulated carrier is continuous in amplitude.. While ham operators use “continuous wave” or “CW” as a term for radiotelegraphy, in reality, all modern radio systems are based on a continuous wave!

There are, of course, other nuances to spark technology, which are best explained with some simple diagrams. Spark technology evolved with time, from simple, fixed spark gap transmitters to quenched and rotary gap systems and, eventually, synchronous rotary gap transmitters in which the spark gap position was synchronized at a multiple of the input frequency at the transformer, thereby synchronizing the gap discharge with the maximum voltage peaks on the transformer output waveform. This increased efficiency (power transfer) and also provided a higher frequency tone when demodulated, thereby providing better copy for a receiving operator.

Contrary to popular myth, spark transmitters did NOT consume an entire band. As the technology evolved, bandwidth decreased. A properly adjusted spark transmitter certainly occupied more bandwidth than a CW transmitter, but it was measured in khz not tens or hundreds of khz. LOL. The radio inspector used a device called a “decremeter” to measure bandwidth of undamped oscillations from spark transmitters to ensure that excessive bandwidth was not utilized.

There’s much more to discuss, of course, but hopefully, this “thumb nail” sketch will help you better understand spark transmitter technology. I have a slide series on the history of radio, which I use in talks to Amateur Radio Clubs, engineering societies and the like, which covers these concepts with easy to understand graphics. — James Wade, International President, Morse Telegraph Club

Below is a compilation from HAncok4 from the Telecom Digest on a slightly related topic:

In Nov 1968 there was a brief mention of Western Union’s new SICOM service, a computerized message switching service for the securities industry:

WESTERN UNION SERVICE FOR SECURITIES INDUSTRY

A computer-controlled system designed for shared use by many firms in the securities industry - providing cross-country communication of buy and sell orders in seconds - is now being operated by Western Union for its first Wall Street customer I Shields & Company.

Called SICOM (Securi ties Industry Communications) Western Union’s new system serves the specialized needs of brokerage firms. The system interconnects a subscribing brokerage firm’s headquarters wire and order rooms, its branches and correspondents, the trading floors, of the New York and American Stock Exchanges, and other special points desired by the subscriber. It provides for the fast transmission of buy-sell orders, execution reports, market news reports, administrative messages and other record information.

Western Union engineered the entire system and provides all components, including computers, circuits, teleprinters, outstation equipment, programming and maintenance. The only equipment located on the premises of a SICOM subscriber is an automatic teleprinter supplied by Western Union.

From photos from other sources, it appeared the system used the Teletype model 28 ASR. This is surprising to me in that the model 28 was a Baudot (5 bit) machine and I would think by then an ASCII machine would’ve been preferred. An average message of 80 characters took 20 seconds to transmit. The initial capacity was 70,000 messages per hour. Messages were switched at the Western Union computer center at Mahwah, NJ.

By way of contrast, at that time, the interstate day telegram rate was $2.25 for the first 15 words, and 9c each additional word. The interstate night letter was $1.70 for the first 100 words and 1.5c for each additional word. At that time, telegram service still represented a good chunk of Western Union’s revenues, although WU sought to transition over to other services like SICOM that had more of a future and profit potential.