Analog command control - was this possible?

In the 1930s, American OO scaler Temple Nieter was working on a control system that sounds like (a basis for) pre-digital control of multiple trains on the same track.
http://americanoo.blogspot.ca/2009/02/oh-oh-heres-oo-part-2.html

I guess he never got this working. My question is, was this feasible?

Radio receivers were established, so a circuit to filter out a given frequency was a familiar idea. But beyond that, how would it work? I'm no electronics expert. The first way I can think of it working is to have the speed-control signal regulate the main power through a transistor - of course, in the 1930s, that would've been a vacuum tube instead. How would reversing work? To control each train independently, you can't reverse track polarity. I don't think you could use a DC pulse as with 3-rail AC systems, since wouldn't that affect all trains likewise?

 

I suspect if it were feasible with stone knives and bearskins, he would have made it work. But if power went to the motor through a control box, reversing polarity would have been the least of his problems.

Interesting find! Human ingenuity always seems to run ahead of the technology that makes it possible. Necessity is the mother and all of that.

Certainly puts the lie to 'build it and they will come'. More like 'build it because someone is already waiting for it.'

 

There was a latter analog command control system in '63 developed by GE called Astrac. It never took root.

http://www.dccwiki.com/ASTRAC

 

Actually, a version of the Astrac was used for years on both the V&O and the Allagheny Midland.

 

Remember CTC-16??

That was more-or-less based on radio control aircraft with the signals sent over the rails.....not entirely analog or digital.

 

Dynatrol I think.

http://www.classicdynatrol.com

 

A couple days after making that post, I was searching for information on Hornby Zero One and I found out about ASTRAC, among others.

Before that first post, the only pre-DCC-standard command control systems I could recall by name were Zero One (digital), Marklin Digital (obvious), Selectrix (digital), and Dynatrol (which I knew nothing about other than that it was limited to something under 20 trains).

It's as I expected. Analog command control is viable, but it took until the 1970s for the technology to be sufficiently reliable, so it didn't have a long time before digital systems arrived. (I don't think radio control vehicles took off much before that time, either.)

 

I belonged to the Penn York HO modular club. They used the Dynatrol system, and it worked very well. We all just got to old to keep hauling all those modules to shows.