[img] Adding shifted keys
MDFS::Info.Comp.Spectrum.Keyboard.Shift/htm Search
Keys that share a common address line or a common data line with
a Shift key can be combined with a simple passive diode circuit.

Common data line (same column)
------------------------------
           ___    +--|>|------Address
Data-------* *----+
                  +--|>|------Address
eg:
 SHIFT+D0: SHIFT A Q  1    0   P ENTER SPACE
                     EDIT DEL          BREAK

SYMBOL+D1: Z  S  W  2 9 O L SYM
           : NOT <> @ ) ; =

Common address line (same row)
------------------------------
           10K
  +5v ---/\/\/\/--+
           ___    +--|<|------Data
Address----* *----+
                  +--|<|------Data
eg:
SYMBOL+A15: B N M SYM   SPACE
            * , .     SYM-SPACE

No common lines
---------------
This needs additional active circuitry.

See also:

Best viewed with Any Browser Valid HTML 4.0! Authored by J.G.Harston - Last update: 22-Nov-2017