Today when I arrived at work I found that the clock outside the office was hanging from the wall by it's wires! No idea why, maybe someone got pissed off with the noise it makes... or maybe that it never showed the correct time...
For those of you that have never come across the Department of Engineering clocks, they are all synchronsied to a master clock. The master clock sends out a pulse down a wire once every minute, which causes the minute hand on every slave clock to advance by one minute. When there's a change in BST or whatever the clock pulses lots and lots to bring the hands around to the correct time...
The observant people who's seen these clocks in action might have noticed that altough the clock is usually wrong, it's only the hour hand that's out and not the minute hand... when looking at the clock I've worked out why... there's a cam which goes around once an hour and pushes up a switch - which diverts which wire the incoming pulse comes from - this is fine if the clock is at the correct time because the master clock also starts send it's minute pulses down the different wire around the hour... if the minute hand is wrong the clock gets pulses from the original wire, which now has extra pulses being sent down it from the master clock - this will bring the clock to the correct minute (big hand pointing to the top) - when it reaches the hour the switch will change back and the clock will work as normal - I think that's really clever! If a minute pulse has been missed for some reason the clock will get corrected on the hour... there is however no way of correcting if the hour has been bollocked up though...
Having played with the clock I know which bit to move to cause the clock to advanced... so now at least our clock is correct. I've resoldered the connections that got broken when it fell from the wall, so now we have a fully functioning and correct clock... until the hour hand gets messed up - which'll should only happen if some breaks the control signal for a period of time! But then at least I know how to fix it now!
Well done if you understood the ramble that I've just written!