U1 - Z80A CPU
U2 - 8Kx8 static RAM Sony 5864, 2186, or equivalent.
U3,U16 - 74LS04 hex NOT gate
U4,U5,U6,U17,U18,U19 - 74LS244 octal tri-state buffers
U7,U20 - 74LS245 or 74LS645 octal tri-state transciever
U8,U9 - 74LS682 address decoder with internal pull-up resistors
U10 - 74LS08 quad AND gate
U11 - 74LS32 quad OR gate
U12 - 74LS139 dual 2-to-4 demultiplexer
U13,U14 - 74LS138 3-to-8 demultiplexer
U15 - 74LS74 dual D flip flop

Sprinkle with .1 uf bypass capacitors as needed.

The board maps into a 32K bank of memory in the PC, the
position of which is selectable via the jumpers on U9.
U8's jumpers permit selection of the I/O port address
that the PC writes to in order to allow the Z80 to run
or to seize control of the RAM chip and map it back into
PC address space.