[GreenKeys] Here is, answer back, WRU

[Jim Haynes]

On Sat, 30 May 2020, John, W9DDD wrote:
> At this point I'll interject an observation I'd had for years but never 
> investigated before.  No documentation from AT&T or Teletype I've ever seen 
> shows a part number between 200000 and 299999.  Well today I specifically 
> looked in a price list (1969 version) for numbers in that range.  I found 
> about a dozen.  They all had a WU suffix.
I remember when all the 100000 part numbers were used up and we jumped to
using 300000 numbers, but I didn't know why.

> So the WU document talks about a single character AB (page 7). Drawing 
> 182426-2 seems to show a solenoid activating one of the keys on a keyboard.
>
I've also seen references to a "V answerback" in some Bell System stuff.
V can be generated by a timer with a duration of two pulse times, so it
generates a start pulse, followed by a single spacing pulse, and the rest
marking.

I think this was used in systems where the outlying stations were polled
by the central controller.  If the station has traffic to send it does so,
and if no traffic it sends the V answerback.  That distinguishes between
a station that is alive and one that for some reason fails to respond.