I don't know if it helps but I did work on terminals in the early 1970's. Before my days at DEC I did work on keyboards. The usual design was a counter going up to 127 or 255. Pressing a key pulled down the data lines for the number representing the value of the key. This was compared with the output of the counter and when they where the same the counter stopped. Thus at this point the counter held the value of the key. Some counters could be shifted (clocked) out serially or you transferred the value to a shift register and serialized the code that way. UARTS could be used like a shift register. (Parallel in serial out.) Rod Smallwood -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Ethan Dicks Sent: 22 May 2007 13:58 To: General Discussion: On-Topic and Off-Topic Posts Subject: CiTOH terminals (was Re: Well,now I've gone and done it... Dragged home more big(ish) iron...) On 5/22/07, Mr Ian Primus <ian_primus at yahoo.com> wrote: I may haev a few CiTOH terminals to drag to VCFmw if there's any interest. Closer to the event, I'll inventory what I have and see if I kept any spare keyboards "just in case", if anyone out there already has a terminal, but can't figure out why their VT100 keyboard doesn't work with it. I remember back in the day, since we had dozens of CiTOH and DEC terminals, looking over the available schematics for both and not being able to figure out how the keyboard works. I think it was a matter of inadequate/fuzzy docs more than anything else. Does anyone know of a good printset to pore over to see the nuts-and-bolts of a VT100-era keyboard? ISTR the crux of it was a 6402-type UART squeezing out the keystrokes at some slow baud rate, but I can't recall any essential details right now. I'm just curious if it's possible to swap a crystal or make a simple, switched change to allow one keyboard to work across both vendor's product lines. We used to have lots of dead keyboard when there was one or two terminals on everyone's desk. Since the company was shrinking at that stage, we never bothered fixing them - we just pulled one off a vacant desk and kept working. The number of working keyboards never shrank below the steadily decreasing size of the staff, so economically, it made sense. I think I only saved working keyboards in that set of 4 van loads, but it's entirely possible I picked up one or two dead ones. Right now, I have to search the pile for a VT100 keyboard to get my DECmate I back up and running so I can press it into service as an RX01/RX02 image archiver and finally whittle down my cartons of floppies. -ethan