Chuck,
not dumb questions at all. I will share a few thoughts that I remember regarding the Associated Press
distribution technology from the early 1960s into the 1980s, as it applied to AP in Georgia and in North
Carolina.
When the local radio station in my hometown in Georgia went on the air in 1960, it was an AP radio
wire subscriber. M-15 RO printer fed via a DC loop from the Southern Bell telco central office about 2-3 miles
away. How the AP circuit got to that telco office? I really don't know, but I suspect there were both DC circuits
and tone on audio circuits between Atlanta and that my hometown in east central Georgia.
Sometime in the late 1960s, the AP in Georgia converted to a tone pack system. The DC circuit was replaced
with a voice grade audio circuit and a Lenkurt 25A single channel tone decoder - audio in DC loop out - was
hooked to the M15.
No doubt the main force in converting from a DC loop system between the local telco office and the
subscriber was cost driven. It was cost effective to convert the entire AP distribution network from
DC loops to the telco, then whatever the telcos used to get the circuits to the telco office nearest the subscribers
and then back to DC loops to the individual TTY machines.
I never visited the AP office in Atlanta, so I never saw what they had first-hand, but I did work in the AP
office in Raleigh as a TTY tech, in 1978. The Raleigh bureau had a rack mounted Lenkurt 25A transmit
equipment unit which could be populated with 25 tone keyers, I never had a manual on the tone layouts, but I
am thinking it was most probably 85 Hz shift.
I mentioned the financial aspect as probably the main motive. Consider a subscriber, that newspaper in
Sioux Falls. No doubt they had a national wire for news. Unless they ignored financial markets, they
had the stock market wire. Probably the sports wire. Since we are discussing the old slow speed TTY
circuits, the stock market wire service was two feeds. The stock market had too much information that
at the slow speed circuit baud rates, it was impossible to feed the entire stock market report to subscribers
on one circuit between the close of markets and the press deadline time for the morning news print cycle.
So, just for those four circuits, in the DC days, the AP would have to pay for four DC circuits, copper pairs
from the telco to the subscriber.
In going to the Lenkurt tone system, the AP needed to have only one voice grade audio pair to the subscriber
location. So the AP would save money on network distribution costs.
Hope this helps a little.
I suspect other folks may have additional information.
73
Sheldon