Another deliberately produced error for you folks! This is what happens when you try to set the mark longer than the period. As you will no doubt recall, SJ Research clocks allow you to set the mark and the period, which is the mark plus the space, so it is possible with them to set an illegal clock speed if the mark is more than the period. On an SJ Research clock box, you would just get No clock errors on the network but with the Bridge clock, you are prevented from setting an illegal clock speed.