Interlocking tower

[knewsom]

In reading through one of the books that I got on the B&O railroad over Xmas, they kept talking about interlocking tower. What is the purpose of the interlocking tower in the steam days and how is a 4 lock and 16 lock tower different?

[jimrice4449]

Interlocking towers were used at junctions and at points with remotely controlled switches. Originally signals and switches were activated by levers which were connected to steel rods, later the levers activated electricaly or pnuematically operated switch machines.
They were called interlocking plants (or towers) because there was a mechanism of steel bars running at right angles to one another having slots and pins that would prevent levers from being thrown to sent up movements that would conflict with one another.
It was common on multi-track Eastern roads to have towers (some RRs called them cabins) spaced every few miles that would direct trains from one track to another on the disptcher's instruction to allow faster trains to run around slower ones and such

[csxengineer98]

QUOTE: Originally posted by jimrice4449

Interlocking towers were used at junctions and at points with remotely controlled switches. Originally signals and switches were activated by levers which were connected to steel rods, later the levers activated electricaly or pnuematically operated switch machines.
They were called interlocking plants (or towers) because there was a mechanism of steel bars running at right angles to one another having slots and pins that would prevent levers from being thrown to sent up movements that would conflict with one another.
It was common on multi-track Eastern roads to have towers (some RRs called them cabins) spaced every few miles that would direct trains from one track to another on the disptcher's instruction to allow faster trains to run around slower ones and such

they also where places that crews would get a new set of train orders from... the tower opp. would hand off new orders to the crew as they want by the tower instructing the train crew on slow orders or train meets and what not... the orders would be issued by the dispatcher... the opp. would "hoop" them up to the engin crew and then another set to the crew on the cabbosse...
csx engineer

[knewsom]

Thanks! Now I can understand a little better the book that I was reading.

[BR60103]

Because of this, you will often find a collection of switches and crossings at a junction called an "interlocking".
You can also get interlocking at a minimal installation. One switch and one signal -- the signal has to be at danger for the switch points to be changed. When the signal is pulled off to clear, the switch can no longer be changed.

[tomikawaTT]

Not a tower, but the absolute minimum in mechanical interlocking.

Home (approach) and start signals were controlled by a couple of humongous counterweighted levers adjacent to the station building, which was only about 9' x 12' in size. These moved the signals (lower quadrant semaphores) by pulling attached wire cables. Where the cables crossed the point linkage of the (manual) turnout to a short branch they were attached to slotted metal bars that ran in a box that protected the workings from debris. Only the appropriate signals could be cleared depending on turnout position, and once a signal was cleared the turnout points could not be moved.

Saw this on the JNR in Kyushu in 1960. The line still operates, but I don't know if the old signals have been replaced.