Random walk in a random environment and rst-passage percolation on trees

A delay line refresh memory stores the bits to be displayed on a visual display means such as a television receiver. A shift register in the feedback loop applies the stored bits back to the input circuit of the memory. Synchronization pulses which occur once each recirculation period are employed to determine which stage of the register to connect back to the memory, that is, to determine the amount of delay which must be inserted in the memory feedback loop to make the stored data synchronous with the synchronization pulses.