Great question on the prosign -…-
Firstly, it's meaning. It has only one real meaning but a couple of uses. The meaning is "separation". It came about originally through telegrams, each part of the telegram (header, body text, and signature) were separated by this prosign. Another usage in marine radio especially is when changing frequency. UP 2 -…- meanings up 2kHz I'm going there now… In amateur radio it is used to separate sentences, or subjects in a conversation. Full stops (periods) .-.-.- and commas - - . . - - were not usually used much in amateur radion in earlier years, -…- is much shorter. Some people combine them (I do sometimes) so e.g. I could use a sentence with a comma and a full stop at the end if my next sentence is on the same subject, then when that subject is addressed or answered, I send -…- This is also useful as a "filler" when thinking what to say next, you may hear more than one -…- possibly as many as 3 or more, if so you know when an operator has run out of thoughts and in a QSK QSO (which should normally be the case in CW) you can simply break in and take over at that point, knowing your not preventing him from telling you something on the same subject that he (or she?) wanted to get off to you :-)
-…- is not actually short fo BT or anything else, the "BT" is only a representation used for prosigns where a prosign would be the same as the letters run together, and this is usually visually represented by a dash on top of the two letters BT, e.g. "end of all messages" could be either SK or VA with a dash over the top and there are various ways of writing these on paper, no particular standard. I used + for end of message, and ] or SK with a lign over the top for end of all messages, some prefer to think of it as VA. But this representation of prosigns is really only normally used for visual or learning purposes, or computers where a prosign could be sent as two characters, i.e. the correct -…- may be sent as BT. This has a pescendent on the teleprinter days (later RTTY) where the -…- prosign was sent as BT.
BT is actually an abbreviation that could be used for but, or perhaps boat, but it's not often used as an abbreviation in my experience.
It is normally on paper, written down as = and that's the way I do it and most operators I know of, unless they're filling out a pre-printed telegram of QTC form. It's much better to use = than a full stop in QSO to save time, unless you are rag chewing. In a normal "rubber stamp" QSO the use of full stops and commas should be avoided. Less expereinced operators, especially when using keyboards, sometimes send 3 or more full stops in a row which can be annoying to the other operator due to the time it takes up without conveying any useful information.
Any other questions on other prosigns or the use of abbrevations, would be more than welcome, we can all learn from this.
By the way, dah dah di di dah dah which normally would be a comma, is used by some marine operators as a "swear word" (insert the worst swear word in your own language here). Usually when used as a swear word it would be send as MEEM dah dah dit dit dah dah with the gaps there and sometimes someone may even clench their fist and pound it on a straight key as you can see it is not a difficult character to send MEEM slowly hitting a straight key with your actual bottom side of your clenched fist HIHI. This swearing usually happened if some operator was really doing annoying things, such as ignoring calls to QRT (Stop Sending!) or "SP" (Silence Period) on 500kHz as between 15 and 18 minutes past each hour, and 45 to 48 minutes past each hour, no calling was allowed, unless SOS or SOS DDD distress or near-distress calls. Usually "SP" was enough to remind such a mistaken operator who forgot to look at the clock before sending, but if he persisted and ignored people, you'd sometimes here people swearing at him. I used it once during the recent RD. Incidentally, greek operators would normally know this sign, as greek ship R/Os used it frequently, but as far as I know e.g. English OPs didn't use it?
If anyone has anything to add, or anything to correct, or further questions, I'd be glad to hear from you too, and hope this answers most of the question for you Gerard. Also, some ham operators use - (-….-) I heard it in DL sometimes, but it's an extra dit, so why bother… and you don't HAVE to write = down as = on paper you could write it as - if you like :-)
