AP always required: Carriage Return Line Feed Letters at the end of each line; this insured that even when the receiving machine falsely jumped into Figures during the carriage return glich, it would be reset into Letters for the new line.
UPI was not that rigorous, and you'd get lines like 5#3178(?492, instead of letters. This occurred often enough that senior UPI editors would sightread it as letters without a pause.
***** Moderator's Note *****
I always thought that the extra "rubout" after the CR/LF was to give older machine a little extra time to swing the type basket all the way to the left. This would compensate for old springs, a dashpot with too little space on the air outlet, or just general gunk, dried grease, etc.
That was standard procedure on the Teletype model 33 as well for the reason you state. If one failed to use the extra rubout, the next character would print in the middle of the line while the carriage was returning.
Curiously, on the model 33 (which was ASCII), while we had a key for RUBOUT (all punches), we did not have a key for a blank column of tape. We had to use multiple keys to create that. We liked to create blank columns for tape leaders and trailers.
As an aside, the purpose of RUBOUT was, as it name suggests, to rub out errors. The tape punch had a manual backspace button on it . If we made a typo, we simply backspaced the punch, hit rubout to cover up the error, and continued on our way.
In the earlier years of Western Union, they used tape printers, that is, the message was typed on thin paper tape, not a page. That made things simpler. If there was an error, the receiving operator, who pasted the tape onto the blank, would simply overpaste the corrected character. Also, there was no need for page control as the receiving operator manually just started a new line or a new page as needed by the message.
Eventually Western Union evolved over to page printers and then computer printers for the remaining message traffic. In my opinion, their computer printers, with the wavy lines, didn't look as dignified as the earlier printers. Likewise, the modernized WU logo (still in use today) didn't look as good.
***** Moderator's Note *****
Some of the the "tape" printers used tape with glue already on it, so ANY moisture that got in the machine would literally glue the tape in place inside the chute, which was, according to the old hands I used to know, easier to fix by completely replacing the tape chute than by trying to remove the tape.
Western Union eventually paid taxi companies to deliver telegram: the one I worked at in 1976 while I was just starting college had a Model
28 RO printer installed for that purpose.
IIRC, the model 33 "tape leader" code was Cntl-Shift-P while holding down the "repeat" key.
When teleprinters came along and replaced Morse circa 1920, the telegraph companies had a choice between tape printers and page printers. A tape printer printed the message on a strip of continuous tape; while a page printer was more like a modern Teletype, printing on a sheet of paper.
The companies chose the tape printer and continued with that until the 1960s. That meant the tape had to pasted onto the telegram blank, a manual step, but there were other advantages. The WUTR of January 1956 explains why:
. larger typeface (tape was eight characters per inch vs. ten char/inch for a page printer).
. ease of correction--errors could simply be pasted over.
. no need for a carriage return, null, and line feed. This improved throughput by 8%.
. tape printers had a lower purchase and maintenance cost.
. tape printers worked better.
. page printers required the operator to count up lines for long telegrams. The early machines had no page eject.
. The elimination of the carriage return and line feed allowed other characters to be used in their place.
When improved machines came along, such as popular workhorse Teletype Model 28, Western Union converted to page printing. However, the character set was slightly different and a conversion effort was required.
The 'last mile' was always a tough spot for Western Union. A hundred years ago they used boys as messengers. Then they got adults and it was expensive. By the 1970s WU wanted out of the telegram business as it was too expensive and inefficient.
Mailgram was a great saver for a while--a win win for the public and WU.
One nice simple feature of the TTY 33 was that the punch had an arrowhead on it. So, when you tore off the tape, it left an arrow, making it easy to see where the tape began and ended.
We had a GE Terminet machine that ran at 300 char/sec. The printer used a band and was quiet. But the tape punch was quite noisy at 300 cps. Making raw papertape stock was a big business in itself. Here are some ads by a paper company:
(Unfortunately, it appears that company is out of business.)