[GreenKeys] W.U. Desk-Fax

[Jones, Douglas W]

The key material about the DeskFax and Teledeltos paper is in the Western Union Technical Review, Vol. 3, No. 1, January 1949.  It's all on line at:
-- http://massis.lcs.mit.edu/archives/technical/western-union-tech-review/03-1/readpg.htm

The first article in the issue is about FAX and Telegraphy, an intro to Western Union's business plan for using the technology.  The next article is about Teledeltos paper, including how it's made and numerous applications.  The third article is about the DeskFax machine.

Someone should snag this material and turn it into a nice PDF document.

The DeskFax article makes it clear that they used polar DC signalling for communication between the central office and the customer, as well as for the sync pulses on each drum revolution.

What is less clear is the use of AM for each scan line.  The DeskFax machine that was photographed on eBay had the interruptor disk, but the machine photographed in the 1949 WU Tech Review didn't have the interruptor disk.  I wonder if the original used a base-band signal, and they only moved to AM because longer lines required it?  Dunno.

The final article in the issue is fun, it's a 1.5 page review of the newly announced Xerographic printing process, speculating that it will become quite important.  It did.

		Doug Jones
		jones at cs.uiowa.edu