There is described an improved system for retaining a video screen in a frame comprising a video screen, a frame for supporting the video screen along at least a portion of the screen’s peripheral edges, and a mechanism for biasing the edges of the screen against the frame to hold the screen in position relative to the frame. The digital signal processing unit has a circuit or program parts which measure the time elapsed since connection of the voltage to the scale. CRC code may be appended to the RLC blocks for error detection. The function returns as a result at least one entity identifier, each entity identifier representing an entity in the network that might provide the replica.