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I am working on an adapter to connect a Xerox Docutech keyboard to a modern computer. This keyboard used a specialized, keyboard/mouse interface that does not have a modern counterpart. I have a schematic for the interface but I am uncertain about a symbol it depicts. As you can see below, the KbrdData + and - lines connect to what looks like a differential pair that generates a single, "DataFromKbrd" signal. They look a bit like op-amps... but I have no idea how those would help in this situation. What exactly are these components? How would I go about making one out of modern parts?

Schematic for Keyboard Mouse Interface

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Based on the vintage, I'd bet an Internet Doughnut that it's a 26LS32 differential receiver. http://www.ti.com/lit/ds/symlink/am26ls32ac.pdf

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  • \$\begingroup\$ One symbol is diff in, se out, so that fits. But the other symbol is se in, diff out. \$\endgroup\$ – The Photon Feb 27 '17 at 20:11
  • \$\begingroup\$ The other symbol is probably the companion 26LS31 differential transmitter \$\endgroup\$ – Lawrence NK1G Feb 27 '17 at 20:12
  • \$\begingroup\$ Thanks, this looks promising. Quick question for ya', though, does the bubble on the negative input of the supposed 26LS31 represent a simple NOT gate or should I look into something else? \$\endgroup\$ – Wingpad Feb 27 '17 at 20:37
  • \$\begingroup\$ There is no input on the transmitter (the 26LS31, if that's what the part is) that has a bubble. Find the datasheet for the transmitter ... The '31 takes a TTL input and generates a differential output, with some specified slew control, and protection. After 30 years, I don't recall the details -- use the datasheet if you need to GENERATE this signal. The '32 takes that differential signal as an input, creating a TTL output. \$\endgroup\$ – Lawrence NK1G Feb 27 '17 at 20:51

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