Abstract: A system for cross conversion of plesiochronous digital hierarchy (PDH) and asynchronous transfer mode (ATM) data is disclosed. A PDH DS3 signal is received and demultiplexed into 28 DS1 data. ATM adaptation layer modules convert the 28 DS1 data to ATM cell streams. The ATM cell streams are multiplexed into a single ATM MUX cell stream and then multiplexed with another cell stream. A router receives the combined multiplexed cell stream, adds a header field, and outputs an ATM cell. The system functions to also convert the ATM cell data to DS3 PDH data using the same basic components.

Abstract: A changeable display unit for use in a sign device which comprises a case containing an electromagnet disposed therein and extending along the opposite sides thereof, the case including a case aperture disposed at the front side thereof, a fixed plate containing a plate aperture disposed at the center thereof, the fixed plate being bent at its center to form wing portions which extend therefrom, the fixed plate being attached to the case so that their respective apertures coincide, a movable plate rotably attached to the fixed plate at the center thereof, the movable plate containing a circular permanent magnet disposed therewithin whereby when the electromagnet is activated, the movable plate is selectively moved between the wing portions of the fixed plate whereby the opposite sides of the movable plate containing desired images are selectively displayed.