[GreenKeys] Model 28 TD - use of dual shaft (LBXD) vs single shaft (LXD)

[John, W9DDD]

I had parts of a FAA table that held one 14TD and one LBXD.  I think at 
one point I found a schematic for that, but don't ask me where it is now.

Were your 2 LBXDs stacked or side by side?

Yes we swapped LXD44 for LXD4 so you would have a spare TD.  Still 
haven't found a cover for the mini base.  Covers seem to be the hardest 
things to find for restorations.

On 7/23/2026 2:18 PM, Nick England wrote:
> Thanks John.
> 1) Yes I have a table-type dual TD with two LBXD. We swapped email and 
> suspected it was FAA although it came from an SK who worked for 
> Norfolk & Western Railway.
>
> 2) I have an AN/UGC-71 multiple address message processor that has an 
> LXD TD with 5-wire output.
> https://youtu.be/WXWpx36RF04
>
> Nick England K4NYW
> Chapel Hill NC
> www.navy-radio.com <http://www.navy-radio.com>
>
> On Thu, Jul 23, 2026 at 2:49 PM John, W9DDD via GreenKeys 
> <greenkeys at mailman.qth.net <mailto:greenkeys at mailman.qth.net>> wrote:
>
>     I've seen references to business machine (IBM?) useage.  The FAA
>     liked
>     them.  They previously used a version of the 14 TD that had a 32
>     (24?)
>     pin slip connector instead the standard 9? pin connector. You could
>     read the tape or you could send 5 bit by the means of external logic.
>     Only one at a time. The two shaft LBXD could do both at the same
>     time.
>     I suspect th FAA was the original reason for the LBXD.
>
>     Did ya mean LX for the 5 wire output?  Or an LXD with the
>     modification
>     kit to add contacts to the reader pins or LD for 5 wire input
>
>     Weren't were looking for some FAA WDs related to the FAA use of
>     same? A
>     WD package for ADIS perhaps labeled as a specification?
>
>     On 7/23/2026 10:38 AM, Nick England via GreenKeys wrote:
>     > I got to wondering about where the dual-shaft TD was used.
>     >
>     > BACKGROUND FYI -
>     > The single-shaft LXD has a single clutch magnet and operates with
>     > direct action from "read the holes" to "key the loop" on every
>     cycle.
>     > The dual shaft LBXD has two clutch magnets with a transmitter shaft
>     > (read the holes) and a distributor shaft (key the loop). They can
>     > operate together (via a contact on the transmitter camshaft
>     triggering
>     > the distributor magnet) or separately - the 5 lines from the
>     > transmitter and 5 lines to the distributor are brought outside so
>     > "multi-wire" data can be read and/or inserted into the serial loop.
>     >
>     > QUESTION
>     > SO, I know the dual shaft versions are used in torn-tape
>     transmitting
>     > equipment where message header characters are inserted between TD
>     > transmitter and distributor. And anywhere else that would be useful.
>     > I'm not clear about where else they would be used.
>     > Al K8WXQ has a 28ASR with LBXD but the 5 lines are just wired
>     straight
>     > from transmitter to distributor (This is its original
>     configuration).
>     > - so why is the LBXD used in that ASR instead of an LXD?
>     >
>     >
>     > Note - there was also a single-shaft LXD with 5-wire output so you
>     > could use that to drive something - I have a piece of torn-tape gear
>     > that recognizes ZCZC, FM, TO, BT, etc, that way.
>     >
>     > So MANY Teletype variants!!!
>     >
>     > Cheers,
>     > Nick England K4NYW
>     > Chapel Hill NC
>     > www.navy-radio.com <http://www.navy-radio.com>
>     > ______________________________________________________________
>     >
>     -- 
>     ---
>     ----
>     The above comments or recommendations are SWAG. Use at your own risk.
>
>     John, W9DDD
>
>     _____________________________________________________________
>

-- 
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The above comments or recommendations are SWAG. Use at your own risk.

John, W9DDD