An addressable memory device for storing blocks of varying length, utilises a write pointer to indicate the address of the next location to which data are to be written and an erase pointer to indicate the address of the next location from which data are to be erased. The first base and the second base have a complementary mounting to suitably mate together. The movable contact has a round dome shape and is made of a resilient metal sheet. A digital signal processor in the back end processes the digital signal and uses a matched filter for data detection.