[HCDX]: RE: Hellschreiber

[Robert Foxworth <rfoxwor1@xxxxxxxxxxxxxxx>]

In this issue of Hard-Core-DX-digest: Volume 04 : Number 1186
    [HCDX]: DX Listening Digest 00-19 Jan 31
** NEW ZEALAND. .<snip>  In the first new show of the
New Year, Adrian Sainsbury finds out about a little known
communication mode - it started life way back in 1927, and was used
during the Spanish Civil War. It almost ceased to exist until an
Auckland Radio Amateur brought it back to life. What do you know
about Hellschreiber?

This was written up in Ham Radio Magazine in the '70's. As I remember it, 
it used a paper tape to print text messages at the receiver, as a replica 
image of the original (sender) tape. There was a rotating detector head 
that would helically optically scan the pre-lettered tape (looking like an 
old Western Union telegram paper tape) at a steep angle, when scanning a 
letter on the tape at the sending end it would send a pulse to the 
receiver, each time the scanner crossed one of the bars of the letter, 
whose sync'ed scanner head would (thermally?)  burn a similar image on the 
receiver's tape. The letters might each have 10 or 15 scan lines through 
them, making them easily readable by eye. This is much like weather maps by 
fax, but there was no greyscale, just B&W.  When the scanning or tape drive 
speeds were not in agreement, the line of letters would "barber-pole" 
across the paper tape. I suppose the receiver guy had to keep it aligned? A 
good benefit was the ability to send reasonably fast data information rates 
across a serial data link of low fidelity. I haven't heard of this in 
years. Surprised anyone remembers it. I suppose hearing it  today on radio 
would just be random rapid short bursts of "fsk" data, but it's a 
non-obvious mode, isn't it?
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