As the pendulum swings to one side or the other, the two arms attached to the pendulum rod at the top, push their respective 'count' wheel around. The arm on the left is shown hanging down in the picture above, this is because I do not use the 6 second output from the clock. As the clock is situated in the lounge it reduces the regular click, click, that these clocks make. As there are also four other master clocks within easy earshot of the this one, all making their own noises, at intervals ranging from 30 seconds to around the hour, other members of the family found it distracting. Speaking personally I fail to see what the problem is. (grins)

The 'count' wheel's have a tooth, which is cut deeper at the requisite place on each wheel, to allow the arm to drop lower and engage an electrical contact, at either a six or 30 second interval.
The two one second contacts, situated at the very top of the rod give out a one second pulse as first one contact, and then the other, are pushed closed by the rod.

For a full illustrated explanation of the impulse system see here.