[GreenKeys] Re: M20-RO

[Sheldon Daitch]

Let me add a little about the AP loop unit.

Unless Ohio was different, for the AP distribution system, from
other states, the AP utilized a Lenkurt tone multiplex system.
I was going to claim it was a 46A system, but maybe my memory is
failing.

That loop unit was a single channel AFSK receiver, that had a 
60 mA loop power supply and a single channel filter for the
appropriate wire service for that machine.

And more from memory, so if I am wrong on a detail or two,
someone add to this.  I think the basic AP Lenkurt system was
a 16 channel AFSK multiplex system, that would allow 16 channels
of data on a voice grade phone line.  

The AP fed the entire tone pack, via the telephone company
distribution system, to the subscriber location, and the
loop unit had the filter for the proper channel that the
subscriber was paying for.  

While different state networks may have had different 
configurations, essentially tone pack had, in the late
1970s, the following services:

  State radio wire - for TV and radio stations
                     5 level

  AM News Cycle - for morning newspapers
                  6 level

  PM News Cycle - for afternoon newspapers
                  6 level

  Stock market report - for newspapers
                  6 level
   (This was actually two circuits, because at
    66 WPM, it took both circuits to feed the 
    complete market close information for the
    morning papers.  One circuit was too slow!)


Depending on the state coverage from the 
regional office, there may be more than one state
radio wire and there also may have been some
state newspaper wires as well.  

73
Sheldon


gil smith wrote:
> 
> Hi Terrance:
> 
> Nice of you to drop me a note.  Yes, the upper/lowercase model 20 is pretty
> rare.  There are two of them that I knew of previously, and now your two
> makes four total known units.
>