A block system is devised and partly made, but is not yet erected.
There was only a single track then, and no block system of signals.
They had the whole district organized on the block system, and they went over each block house by house.
We may now pass to the working of the block system of signalling trains from station to station on one line of a double track.
"I don't know what is meant by the block system," added Mrs. Belgrave.