I won't bore you with history, but we used to have five 50-minute
periods per week for our (calculus -based) General Physics lecture
courses. Each one-week block, I used two periods for
lecture-demonstration, two periods for problem solving, and one
period for a test. During the lecture-demonstration periods, I'd put
my notes on the board and the students would (mostly) copy them.
Then our chairman decided to cut out a period.
So I have cut the two lecture-demonstration periods back to one. Now
I have my notes available to the classes on line
(www.ncat.edu/~gpii). During the first period of a block, I project
those notes on the screen and talk and demonstrate my way through
them.
This seems to be working well. The students are happy and their
median grades have shown no large change one way or the other.