[GreenKeys] AP Model 15 information

[Dave Emery]

On Mon, Feb 23, 2004 at 10:59:56PM -0500, sdaitch@ibb.gov wrote:
> I never saw any of the polar relays in use with the telco DC loop, but
> I admit my experience was with only one AP situation, the radio station in
> my home town.

	There definately was in our situation.   And I'd actually
imagine that it might be rather difficult to handle the inductance
of two or three printers (may have been as many as three on our circuit)
and quite a few miles of wire all one one loop.


>  The conversion from DC to tone apparently occurred in the mid-60s or
> so.

	The UPI went to tone in upstate NY (where I was) in the summer
of 1969.   They actually installed the audio line for the mux almost
a year earlier in 1968 (it had an elaborate termination and equalizer box 
associated with it in our wiring closet - data lines in that era
were serious business).   It sat idle for a long time for some reason.

>  Maybe the loop length was short enough to use on-off DC.
>  I do rememeber, tho, that the DC pulses could be heard between the ringing
>  current tones to the station, when you would call them on the phone.  

	I remember noticing lots of TTY to phone interferences in various
places in that era - notably the local bus station had a printer and every
time it printed a message one heard very LOUD clicks on the payphone there.

	I don't remember if we had any problem with the TTY signal getting
into audio lines in the studio - don't think so, which tends to confirm
the polar relay in the machine memory.
	

> The Lenkurt system was used well into the 1980s, but I haven't had a
> good technical discussion with anyone from AP in many years, so I can't
> tell you how AP is distributing to radio stations these days.  I know
> the AP was going heavily into satellite distribution, and maybe they are
> totally off the telco system these days.

	At one time in the 90s they were on a transponder on S-4 C band
for their feeds, but last I heard it was not mostly if not entirely done
over Internet connections (VPNs).   There was a time both they and the
UPI experimented with Equatorial Communications spread spectrum modems
on satellite (early VSATs).    I think the UPI used some version of
those into the 90s in fact.    And for quite a few years in the 80s and
maybe even early 90s there were MCPC narrow band FM-FDM signals aimed at
radio stations on satellite that carried a mux with the standard VFT
tone packs with radio/TV wires  above program audio for UPI and maybe AP
radio news.


> The Extel AH series printers had room for and sometimes did have their
> own tone convertoer buillt in, and it was smaller than the Lenkurt o\box
> system.>  > their own 

	I had one of those in my collection for a while back then.
Didn't have the tone converter though...

	They were common replacements for model 15s and 28s in financial
wire service applications.   And lots of financial wires (like Dow Jones)
were also distributed on tone packs similar to the AP and UPI ones, so
there was a market for such a design with an integrated modem.

	And I ran across some of them in newsrooms where they had finally
replaced the old model 15s.

-- 
   Dave Emery N1PRE,  die@dieconsulting.com  DIE Consulting, Weston, Mass 02493