Steve:
The electronic switch was used to view two signals on a
single trace scope. It was analagous to a single pole
double throw switch. The positioning control you mentioned was
used to locate or position the scope traces so they could
be viewed for best advantage.
The previous answer is right on. Heathkit had a more modern,
solid-state model. I don't remember if Knight-Kit did also.
In addition, most electronic switches had an output that went
to the external trigger input of the scope so that you could
select which of the two signals you wanted to trigger on (or
"sync to" if it was an older recurrent sweep scope). These
little switches provided "CHOP" dual trace operation, so were
for lower frequencies only or you'd start seeing the "sampling"
of the individual channels.
Although they aren't too useful today with the average scope already
having two channels, there are a lot of circuits out there that
are similar for providing 8 or 16 channels for viewing multiple
channels of logic signals -- an old idea updated.
Dean