> Paper tape is, of course, something like a narrow player piano roll, 
> and
> could be read the same way.


Lonnng ago I and a friend made a paper tape reader that worked very 
well.
9 opto transistors -  8 r data and 1 for sync track.
Tape simply went through a guide over the transistors and was hand 
pulled.
Tape holes were spaced at 0.1"

While they were miniature, the transistors were > 0.1" wide so were 
too wide to stack side by side across the tape width so they were 
arranged in 2 banks of 5 and 4 a few data words offset and the bits 
were shuffled into their correct bytes after reading. A tungsten lamp 
provided illumination - afair room light would usually do but data 
integrity could be optimised by adjusting illumination level. HP's 
then practice of using black tape made sense.

As slow or as fast as you could go data read OK afair. From dim memory 
you could pull tape through at say 1 metre/second. (Probably faster 
but ripping the tape was to be avoided). At 10 bits per inch that's 36 
inch/second x 10 bits/inch  x 8 bits_parallel = 2880 = say about 3 
kbps. Given that "usual" data rates then were KSR33 with a 1200/75 
modem and a hammering paper tape punch or 300/300 modems, that was a 
very acceptable data rate.

The reason for having paper tape was that

1.   It provided non volatile "mass storage" for an analysis machine 
when any sort of storage was expensive and essentially unavailable on 
my budget.

2.    It was the only realistic way of getting data from a 
microprocessor based system (MC6802) into the available Burroughs 
B6700 mainframe computer for processing. Writing to magnetic tape was 
not an option (although I had previously made a 6802 based 8 track 
magnetic tape reader and could have written tapes if hardware had been 
available). (The only way to get a 4 MHz clocked 6802  (1 MHz system 
clock) to go fast enough to read the 20,000 data words per second from 
the tape had been to push data onto the processor's stack (usually 
mainly intended for  subroutine handling on the 6800)

AFAIR I acquired a tape punch from the local rubbish tip and cleaned 
it up well enough to use. Operation was 110 VDC afair and I used reed 
relays to drive it. It worked. The reader was used to allow reading of 
the data tapes which I had written.

Those were the days.
Fortunately, they've gone :-).

        Russell 

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