[GreenKeys] Early Fax Machine

[Jim Haynes]

On Fri, 30 Dec 2016, Jones, Douglas W wrote:
>
> Looking at the last photo on the E-bay page, there's a chopper disk in 
> the light path from the paper to the photocell.  This looks like it will 
> chop the light beam at an audio frequency.  That means that it's highly 
> likely that the signal will look like an audio signal on the wire, so it 
> will probably work over voice-grade phone lines.

There is a chopper disk to turn the fax signal into AC so it can be
amplified with AC amplifiers.  However I believe the control signals
are dependent on DC connectivity between the machine and the W.U. office.
Again, Western Union Technical Review should have a pretty complete story.