[R-1051] R-1051 Speakers

[David I. Emery]

On Thu, Nov 21, 2019 at 10:17:52AM -0500, paul swed wrote:
> UCC1 another memory from the past. I do have a operational ura17. That was
> a cadillac when at home I used home brew demodulators as a young ham. The
> UCC1 also taught me how to home brew narrow band demods for the AP and UPI
> wire services in the early 80s through 1990. They were muxed at that time.

	The 120 Hz spaced VFT mux FSK wire line signals used to
distribute the low speed TTY AP and UPI wires directly to customers were
put in service in the mid to later 60s FWIW... around 68 in upper NY
state IIRC.   They replaced DC telegraph loops on copper pairs (with
polar relays to key the magnets in the TTY machines) with a transistorized
FSK demod and solid state loop keyer that sat on the table under the
machine and was fed the VFT mux audio off a leased (and conditioned)
telephone private line voice grade data circuit (also on a copper pair).
  
	The channel (eg wire) that these demods tuned was typically set
by plug in filters and discriminator modules.. though some later
hardware used a superhetrodyne architecture and a PLL locked LO to allow
channel changes with DIP switches.

	FWIW it is also notable that - internally in telco plant -
similar carrier telegraph circuits on voice grade channels were used as
long ago as the 1930s though some of these were AM (OOK) rather than
FSK.  And before that WU and other telegraph companies used various
similar audio FDM multiplexing as well as the more common TDM on
various telegraph lines.

	There was an era when some of these wire service wireline VFT
mux signals were uplinked as audio (itself muxed) on various satellites
carrying  AP and UPI and other wire services ... these days there are
actually still some AP text news streams on the AP TV MCPC carriers on
various world wide C band birds, but of course as streams on a digital
PID in an IP oriented format.  

	And in a few places there was some experimentation in the 70s
with distribution of wire service VFT mux on FM SCA subcarriers...
which died out as more folks got access through various satellite paths.

-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."