deskthority

I found a NIB IBM PC/XT keyboard that at first I thought might be a type 1 keyboard, but when I received it I realized it was an EMR. Interestingly, it had the "Personal Computer" badge instead of the "EMR Keyboard" badge. It has a very strong smell which reminded me of the "Pingmaster" 6113442 / 6112884 keyboards.

To the pictures...





Edit: Added this note that was included in the box:

Impressive. They really do seal the circuitry!

Still seems a bit suspect to me, though. Surely capsense — for all its strengths — is a finicky, emissive bugger when it comes to the "pad card" itself? (IBM-speak for the main PCB behind the barrels.) If you're observing EMR voodoo, that won't do, not right under the keys! (Hell, with anything but a rock solid earth, Model Fs can go seriously apeshit, let me tell you!)

Wasn't that the reason for the Oak switch industrial XT?

Wow. NIB too. Awesome find!

Maybe the seller translanted the assembly into a different case? The big thick cable and the potting ceramic on the controller do make it look obvious that it was TEMPEST-proofed...

Very similar to mine, except mine has a far messier controller potting job. http://imgur.com/a/WCJzA

Not bad though, certainly cleaner than mine

The EMI has a metal top does it not ?

Muirium wrote: ↑Impressive. They really do seal the circuitry!

Still seems a bit suspect to me, though. Surely capsense — for all its strengths — is a finicky, emissive bugger when it comes to the "pad card" itself? (IBM-speak for the main PCB behind the barrels.) If you're observing EMR voodoo, that won't do, not right under the keys! (Hell, with anything but a rock solid earth, Model Fs can go seriously apeshit, let me tell you!)

Wasn't that the reason for the Oak switch industrial XT?

The EMR (Electro-magnetic Radiation) keyboard was built as to meet TEMPEST certification, with the goal of preventing emissions from the keyboard, not the other way around. During the cold war, The Russians (and others) had developed equipment the could intercept and amplify emissions from electronics and recover protected information. This could be done at considerable distances. IBM built complete EMR PC's that were used by government, industry and the military. These machines were referred to as the Tempest PC or TPC family or conputers. According to IBM docs, there was also an EMR version of the F122.

The brown coating is conductive and has slight resistance that will absorb and dissipate emissions if properly grounded.

I talked to a knowledgeable friend with relevant expertise and asked him about the unshielded portion of the PCB. He said that the key portion of the keyboard does not need to be shielded. There are no data signals passing through the un-shielded portion of the pcb and the capacitive pad arrangement generates very low power emissions that could not be detected at distances of more than a few feet. He said that proper pad design and layout can reduce emissions even further.

andrewjoy wrote: ↑The EMI has a metal top does it not ?

No, its the same case as any other.

I had a Zenith 80286 desktop unit that was Tempest, from the govt auctions years ago. Weighed 50 pounds. 60 screws held the cover in place. The hdd had a label that said "Not valid past 60 Gs". It required a Tempest keyboard, which fortunately I acquired in a different batch. A fellow from Austin got them several years ago.

If a computer was not built to Tempest standards, you could actually tune an AM radio to an "off" frequency and hear the tones the keyboard emitted as the typist worked.

Wow,first to see the NIB. Excellent found!
So, what is the difference of IBM EMR Keyboard and the IBM 5150 keyboard?

EMR keyboard has a potted controller, thicker cable and a ground strap on the cable. Really the only differences as far as I can tell. There's also an EMR II board which (all that I've heard of) have a different connector all together.

elecplus wrote: ↑I had a Zenith 80286 desktop unit that was Tempest, from the govt auctions years ago. Weighed 50 pounds. 60 screws held the cover in place. The hdd had a label that said "Not valid past 60 Gs". It required a Tempest keyboard, which fortunately I acquired in a different batch. A fellow from Austin got them several years ago.

If a computer was not built to Tempest standards, you could actually tune an AM radio to an "off" frequency and hear the tones the keyboard emitted as the typist worked.

I wonder if it's sort of the intersection of "cold war paranoia" and "poor best practices regarding design for RFI in typical consumer hardware." I recall reading, for example, the European-spec Commodore 128D couldn't meet US RF interference standards; the model they sold here has a metal case instead of plastic to compensate.

I'd expect they ended up having to do a better job at controlling emissions as small computers became a mainstream thing, because people would get pissed if they couldn't tune any radio or TV station because their neigbours all had computers. OTOH, I know that over the years, different hardware I've owned has annoyed family members with their radio and TV.