Front panel switches - what did they do?

Brent Hilpert hilpert at
Tue May 24 16:09:14 CDT 2016

On 2016-May-24, at 1:49 PM, Eric Smith wrote:
> On Tue, May 24, 2016 at 1:49 PM, Brent Hilpert <hilpert at> wrote:
>> We were discussing this last year, perhaps I'm being pedantic but I would note that while, as you say, there is commonality of principle in use of induction and the selective weave to represent the data, TROS and core rope (of the sort used in the AGC) also have differences in their principles of operation - they're not just physical variations on each other.
> My understanding is that both used drive lines that either went
> through the transformer, or around it, to either couple a drive line
> to a sense line, or not. In the case of CRM, the wires are essentially
> braided with the cores, while in TROS, holes are punched in strips of
> flex circuit to break one of the two paths the drive line can take for
> each sense position, and the transformer core is a two-part
> rectangular thing rather than a little toroid.
> If I'm wrong, or missing some fine point distinguishing them, I'd
> welcome corrections or additional information.

Yes, I examined this in some detail last year after mention on the list, and wrote it up:

The short of it is, schemes like TROS are using simple induction / transformer principles with a selective weave through the transformer cores to represent the data. In contrast, (AGC-style) core ropes are using switching cores and core-logic principles to also do the 1-of-n address decoding within the cores. The address decoding requires a varied weave of address wires through the cores, in addition to the selective weave for the data. The read/access operation also becomes far more complex for the AGC-style core rope.

More information about the cctalk mailing list