The Fialka's keyboard is a rather complex mechanical structure.
When pressing a key, one of the 30 switches of the switch array
are engaged. The switch array is located behind the keyboard and is
part of the drum assembly.
The drawing below shows the switch array when seen from the front
of the machine. All switches are mounted onto an axle and have one
central contact (on top) that can be moved between two static contacts
(normally-open and normally-closed).
A switch can be engaged by the keyboard, by pushing a metal arm to
one of the circular pads at the bottom.
As you can see in this drawing, all switches are sorted in the order
of the Fialka's alphabet (i.e. in the same order as on the wheels).
The normally-closed contacts are all connected to the Diode Matrix
that acts as a 30-to-5 encoder.
The normally-open contacts are connected to the input
of the card reader. Please note that, although all contacts
on the Switch Array are nicely sorted in the order of the alphabet,
they are connected in a scrambled manner
to the input terminals of the card reader.