That encoder in your 2563A is only used to determine printbar position.
A simple free-running ac motor & crankshaft move the bar but can't 
position it.
The print data is passed over copper wire ribbon cables.
Sorry but nothing amazing there.

Bob J. -- Ideal Computer Services


Johnson, Tracy wrote:

>A 3rd party maintenance person come into clean and do preventive
>maintenance on one of my HP256x (2563A to be exact) printers today.
>Whilst observing and chit-chatting he was setting the gap between the
>printer core and the static encoder.
>
>Now I don't rightly know how a static encoder works.  But from reading
>the manual and observation, it transmits data between the encoder and
>the core bar via that gap at a frequency of 42.9KHz.  
>
>Previously I had never thought how the data signal got to the core bar.
>Without a low power radio signal, (in my train of thought) there had to
>be some amazing ribbon cable technology that could withstand all that
>vibration for 25 years.
>
>I pondered at what an amazing device that static encoder is and what
>kind of award the engineer should have got who thought of it?
>
>HP doesn't make stuff like this anymore.
>
>I was also thinking that if a similar device were to be built today,
>someone would have used infrared or a laser between the data stream and
>the core bar.
>
>(Or two iPhones next to each other?  No excuse for not wasting bandwidth
>these days.)
>
>Tracy Johnson
>Office 1-757-766-4318
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>
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