[GreenKeys] FAA dates

[jhaynes@alumni.uark.edu]

I've been trying to get around to answering this question.

The C.A.A., forerunner of the F.A.A. was into Teletype quite early for
aviation weather reports.  I don't have a starting date.  In the 1940s
they improved the system with ASID - Automatic Station Identification
Device.  This was a box of relays, not made by Teletype, that worked with
a modified Teletype XD that had the ability to run the distributor without
feeding tape and had the tape sensing contacts and the distributor 
segments brought out separately.  I believe a very similar XD was used
with the 81D1 and some other switching systems, at originating stations.
(An originating station is usually a station for originating messages
right at the switching center, so you aren't limited to the single wire
line between the center and the station.)

ASID allowed the operator to turn on his tape reader anytime during the
transmission from the previous station in turn.  When the line went idle
it would start the distributor, send the station identification letters
from relays, and then send the tape containing the weather report.

I have a manual dated 1948 on Teletype Sequential Control (SECO) for
the C.A.A.  SECO provided for a tape for polling the outlying stations.
At each outlying station there was a SOTUS to detect the polling and
send the weather tape.  Some arrangemently locally engineered by the
C.A.A. provided for copying selected messages from one area circuit to
another, using FRXD machines controlled by the SOTUS.

Then about 1959 the F.A.A. contracted with Teletype for a replacement
weather system called ADIS, Automatic Data Interchange System.  This was
a major project, brought on partly by the arrival of jet airliners and
hence the need to get transcontinental weather data shipped around faster.
Principal features of ADIS:
  area circuits upgraded to 100 WPM using Model 28 equipment (and the
    Model 28 stuntbox replacing the SOTUS)
  area circuits are polled by a stepping-switch unit (not made by 
    Teletype) called APULS, Automatic Programming Unit, Low Speed
  a 600 wpm national backbone circuit linking all the area circuits.
  traffic from the area circuits goes on to the backbone at 
    interchange centers using low-to-high speed converters,
    consisting of Model 28 reperforators and BX high speed readers
    (and big reels for the tape supply and takeup)
  interchange centers are polled to transmit by a stepping switch
    APUHS, Automatic Programming Unit, High Speed
  traffic on the backbone is selectively copied on to high-to-low
    speed converters at the interchange centers, consisting of BRPE
    high speed punches and LBXD readers
  a magnetic core rope decoder at the interchange center recognizes
    the station identification letters in the backbone traffic.  A
    big plugboard with diode plugs turns on selected high-to-low 
    converters to copy traffic from the backbone and repeat it into
    the area circuits

Following installation of ADIS the F.A.A. contracted with Teletype for
a message switching system called BDIS.  BDIS is sort of a pun on ADIS.
ADIS was for the weather service, called Service A, and BDIS was for the
flight plan and message system called Service B.  BDIS used a similar
architecture to ADIS, a high speed backbone and low speed area circuits.
The high speed part was spiffed up with DRPE tuned-reed punches and CX
tape readers.  Since messages in BDIS are point-to-point the Model 28
stuntbox is used to suppress printing on messages not needed at a
particular station.  There were some things called message rejectors;
and I haven't been able so far to find out what they did.  A guess is
that they prevented messages from going on to the backbone if they
didn't need to, such as messages where the origin and destination are
on the same area circuit.

Then there was to be a system called CODIS, of similar architecture for
Service C and Service O.  This system was cancelled during development
as the F.A.A. chose instead to use a computer-technology switcher.  I
think they used a Collins C-8400 computer.
--

jhaynes at alumni dot uark dot edu