Mastering the telex service involved learning a new language of compressed words and acronyms, methods for adding emotion into a telex “conversation” and other etiquette.
The first, and most important, lesson was that telex messaging was a half-duplex operation, much like an address and reply conversation. Attempting to type a message while the other operator was sending resulted in characters from both operators being mixed unintelligibly and quickly led to mechanical keyboard lockups as mechanical buffers overflowed.
An interactive telex call involved alternating messages between the two parties with each operator indicating that they had finished transmitting by sending + at the end of their last word or ?+ on the last line which invited a response.
If the sender wanted to indicate that they were finished, they would end with ++ which invited the other party to confirm they had finished with +++ The last lines of a telex conversation would look like this:
TKS CU THEN ++
RGR CUL +++
followed by an exchange of answerback codes.
If one party needed to stop for some reason, they would transmit MOM PSE (one moment please) which let the other party know they were still involved in the conversation but otherwise engaged.
If they were thinking of a response, they would often alternately hit the numbers and letters keys which would cause the other telex machine to mechanically switch between numbers and letters mode without printing unnecessary characters. This was a highly expressive action as the receiving party would see the print head rotating indecisively back and forth without printing – a clear indication of uncertainty if ever there was one.
Anger was often expressed by several hits on the bell key or typing over the top of the other party – a very rude gesture. Growing anger could also be expressed by deliberately typing characters at a regular but slow rate such as DO YOU AGREE??? in letters sent at 1 second intervals.
With its origins in morse, many radio operator terms ended up in daily use on the telex service. RGR was, of course, “roger” for agreement. STBY or SBY meant “standby” or “please wait.” PSE was “please,” and TKU was “thankyou,” or TKS was “thanks.” MNG was “morning,” GM was “good morning,” TMW was “tomorrow,” and CUL was “see you later.” Operators who became known to each other over time would often refer to each other as OM – “old man” – such as in CU TMW OM.
GA had to be read in context, as it could mean both go ahead and good afternoon, but was not a challenge for an experienced operator. GA+ obviously meant “go ahead” as it was followed by one or two + characters indicating the sender had handed over to the other party. GA OM at the beginning of a message was an abbreviation for “good afternoon, old man,” and would usually be followed by more text.
In the early days of the Internet, when it was evolving from a text-based medium, many of these conventions entered into the etiquette of the time, and became known as “netiquette.” Sadly, much of the netiquette has now fallen into disuse.