22 Jun
2025
22 Jun
'25
4:04 a.m.
On 22/06/2025 10:26, Tony Duell via cctalk wrote:
On Sun, Jun 22, 2025 at 9:44 AM Frank Leonhardt via
cctalk
<cctalk(a)classiccmp.org> wrote:
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.
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 :-)