On Fri, 1 Mar 2002, Douglas Butler wrote:

> I'll bet it was just paper tape and mechanical finger contacts.  The
> ASR33 teletypes I once used worked that way.  The fingers were
> retracted, the tape advanced, the fingers extended and found holes or
> not, cycle repeats faster than you can see.  Centainly fast enough for
> scrolling signs.  The tape would last a few hours, by which time the
> news would change anyway.  The key is that the fingers never touch the
> edges of the holes.  The contacts driven by the fingers could probably
> drive the light bulbs directly, no relays or other amplifiers (1/4A @
> 110V for a 25W bulb).

The old IBM punch card equipment used conductive rollers under the card,
and steel brushes made from fine (30-ish ga.) wire.  In fact, the printer
carriages on the old 1403 printers used paper tape the same way, they'd
last for years.  They might've done it that way.  You could possibly even
use a large drum with multiple sets of brushes...

Dale

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