On 22/06/2025 10:26, Tony Duell via cctalk wrote:
On Sun, Jun 22, 2025 at 9:44 AM Frank Leonhardt via cctalk
<[email protected]> wrote:
Lack of paper tape is was why I was asking about a replacement.
The same goes for TTY replacement.
Which is why I suggested cassette tape as the closest practical
contemporary equivalent :-)
There was a version of the Silent 700 terminal which had a unit on top
containing 2 digital cassette drives [1]. These 'replaced' the paper
tape punch and reader of other ASR terminals, I think you could save
data from either the line or keyboard onto a caseette (equivelent of
punching paper tape), copy from one to the other editing as you go and
send the data from cassette to the line or printer (equvalent of
reading a paper tape).
[1] Same dimensions as a normal audio Compact Cassette but with a
different grade of tape (higher coercivity?). You can identify the
cassettes by the slightly off-centre notch in the rear edge.
I never saw one of those, but that's the sort of thing I was as talking
about. The BIOS on a lot of the 8-bit micro boards I used was agnostic
as to whether it was a cassette tape interface or serial reader/punch.
The only snag was that the cassette couldn't start and stop on a
per-character basis so you couldn't realistically make a tape by keying
as you could with paper, and you had to insert nulls on the end of a CR
to allow time for processing a line that had just been input. Microsoft
BASIC had a NULL command to set the number of nulls required. So how, if
it could, did this Silent 700 make a keyed tape?
But the real beauty of a Kansas City tape interface is you can build it
yourself and use any old tape recorder. I just checked and they're £32
new on Amazon, and the cassettes are still being made. The cheapest way
to get that authentic 1970's feeling.
The schematics are available here: https://osiweb.org/manuals/600revB.pdf
Sheet 7. It doesn't label the chips, but they are U62 7404 (inverters),
U63 7474 (D-type Flip Flops), U64 7476 (JK Flop Flops), U66 CA3130 (op
amp). Plus something to generate the clock and some resistors and
capacitors. All still easily available.
