"1" points to a set of contacts used to create electrical pulses.
Notice the odd shaped device, "a cam", in the center of the dial.
When it turns, it pushed the leaves where the contacts are mounted, APART.
As the cam continues to turn, the contacts CLOSE again because the leafs have a spring tension on them.
This action has created a dial pulse. that pulse is registered in telephone office switching equipment.
In dialing a 5, the gears incased inside of housing, force the cam to spin 5 times, sending 5 pulses.
There is more to this dialing explanation but only this point is the subject of this web page.