[GreenKeys] [die at dieconsulting.com: Re: [Bulk] Re: Telephoto machines?]

[Richard Knoppow]

      FWIW a Google search for Teledeltos got a lot of hits mostly about 
applications other than FAX.   However, evidently the paper could be 
used to produce a half-tone image in the same fashion as done for ink on 
paper printing by using variable size dots.  It seems to me that this or 
some similar paper was also used for chart recorders.

On 6/29/2015 9:16 PM, David I. Emery wrote:
> On Mon, Jun 29, 2015 at 03:34:44PM -0500, Jim Haynes wrote:
>> Western Union developed an electrosensitive recording paper in the 1930s,
>> which they named Teledeltos.  There was a black conductive inner layer,
>> with a metallic coating on the back and a grayish-white coating on the
>> front.  Supposedly it was electrically conductive all the way through, so
>> that a voltage applied across it would ablate the front coating to
>> expose the black interior.  So maybe it wasn't necessary to spark, but
>> sparking and smoke happened anyway.  As the ingredients were a secret
>> one could worry whether it emitted toxic fumes.
> 	This stuff was common in some 1940s and 1950s military weather
> fax machines - which used big sheets of it wrapped around a fairly large
> drum.
>
> 	As I understood it, the coating on the front of the paper  was
> mostly zinc oxide... with a carbon black impregnated paper backing.
>
> 	The stylus was thin tungsten wire which is very very hard and
> resistant to high temperatures (needed to survive the arcing process).
>
> 	A machine I had used AC excitation... transformer coupled as I
> remember it...
>
> 	And indeed it did make smoke (and probably other toxic fumes)...
> and also quite a bit of noise (the AC carrier frequency was clearly
> audible).
>
> 	Any gray scale involved was very very limited at best... but it
> did work OK for black and white weather maps...
>

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL